What do you take in to account when picking pokemon for a party?

Essentially, I'm making a program that will store information about the pokemon in the parties you want to create.

It's really early on right now, so it focuses on picking pokemon and their moves, and then analyzing the types in your party (both of the pokemon and the moves they are using).
With this information it will 'analyze' which types your party is strong/weak to, taking in to account the types of your pokemon (and what moves they are weak/strong to) as well as the types of the moves (and which types they are weak/strong against)

There is a LOT more planned, involving EVs, abilities, natures, breeding plans, etc, but I'm lacking a bit on the analysis part.

Can you guys tell me what you would like to see from an automated analysis?
What do you take in to account when making your party?
What calculations (if any) do you do, that you would rather have a computer automatically do for you?

Edit:
For more information on the program I'm talking about, which is called 'PokePP' for 'Pokemon Party Planner' have a look at these links to get an idea of what I'm trying to accomplish:
Progress Blog: pokepp.wikidot.com
Feedback Page: pokepp-feedback.wikidot.com

From an automated program I think maybe a couple results of Pokemon that can be particularly difficult for your team would be helpful. Obviously not every single Pokemon of a certain type, but perhaps Pokemon based on their moves, abilites, etc. that could be trouble.

When making a party I try to look for diversity. Trying to cover all the weaknesses and have a balanced team is, I think, essential in battling. And with a program like this, it'd be fun to try and find a "perfect" team.

Thanks for the suggestion!
And it was that concept of 'the perfect team' that got me interested in this, hopefully it will actually work out that way XD

Also: I edited the first post to include a couple links to some of the online pages I'm setting up, hopefully these can be useful =P
(though you'll have to copy/paste as I'm too new to the forum)

Really when I am building a party I don't put much thought into it other than, "oh I like this Pokemon, so I'll use it on this playthrough". Yes, sometimes my teams are unbalanced, but it is just in-game so I can still be successful with a team of Pokemon that I just like rather than a team that I strategically planned.

Obviously well rounded teams, but I like to pick teams with members that have high Defense and SpDefense stats. Most of the NPC's pokemon are under leveled, so you can take them out easy even with pokemon that don't have too high of an Attack or SpAttack stat. Some examples of good team Pokemon(in my opinion) are,
Scrafty, Cloyster, Skarmory, Leafeon, Umbreon, Dusknoir, Mr. Mime, and Hitmonlee
If I were to re-do my 5th gen team, it would most likely contain:
Serperior, Skarmory, Dusknoir, Scrafty, Umbreon, and Mr. Mime.
Also, a wide variety of attacks (even ones that aren't STAB) is critical for facing the Elite 4 and the gyms.

I mainly like to use Pokemon I like, but also ones that are good in battle by having good abilities, movepools and such. My teams were heavily unbalanced back when I first played Pokemon games especially Ruby because I doubled up on types too much. Thank god I learned that lesson when making teams in future games. I also like to try and get every strength and weakness covered.

Honestly for me, it's mostly about aesthetics. I just pick Pokemon that I think look cool and go with them. Though, I do sometimes go by the Pokemon I like for their backgrounds/typing, etc. Normally I just like the cool looking ones on my team because I'm rather shallow in that sense. :P

Haha, so a lot of people like aesthetics then? That's one of the reasons I included the sprites in my program for the visual appeal, but right now its only using the latest sprites. So an additional question for those going for 'looks':
If you were to use my program, would you prefer images that are from the latest game? or their 'original' game sprites?
For example do you want the original, pixel based charmander from reb/blue, or the newer, higher resolution sprite used in 5th gen games?

Types. Mainly.

Side factors include, Pokémon appearance and gender.

I never have the same type, but other than that I am not fussed

I just choose whatever Pokemon I feel like using while trying to have a balanced team. It doesn't work all the time (in fact more often than not I seem to have a big weakness in my team) but as long as I have fun in game I really don't care what my team ends up to be. Just means the game is a little more difficult and that's fine!

I usually start off with pokemon that I like the most, and then try to compliment their types with pokemon that I'm overall-okay with.

Example in White, I knew before playing that I wanted Samurott, Whimsicott, and Excadrill. I then balanced out my team with a fire-type, electric-type, and dark-type, none of which conflicted with my other pokemon.

Shrew said:

I usually start off with pokemon that I like the most, and then try to compliment their types with pokemon that I'm overall-okay with.

Example in White, I knew before playing that I wanted Samurott, Whimsicott, and Excadrill. I then balanced out my team with a fire-type, electric-type, and dark-type, none of which conflicted with my other pokemon.

Click to expand...

I tend to do that too, I'll have my favourites that I'll just have to have (even if they aren't too good), and then I have to fill in the rest of the team to cover the holes.
That's one of the things I made my program do first as I noticed I do it manually a lot, get farther in the game to find I have a big ol' hole I missed that only appeared in Elite Four (or battle arena)

Looks and stats.

Must have a Fire Pokémon (a good one, can't play DP without Infernape really).

Must have a Dark Pokémon if applicable.

I usually use offensive Pokémon.

I look for their looks and their movepool before deciding putting it on my team.

some ppl are mentioning movesets as a big factor. would abilities that pair with movesets be a big factor? for example I like to use an aggron with heavy metal ability(doubles aggrons weight) and heavy slam (power increases the heavier the pokemon). would this combo override a pokemon with a better moveset or movepool? (I have him in my party for other reasons too since steel is the best ranked defense so far and since his defensive skills are so high, but for the sake of this question assume that moves and abilities arethe only factor in choosing)

I don't put too much stock into it, honestly. I just make sure that I'm using Pokemon I want to use and that it comes out balanced. Sometimes I might use two Pokemon of one type if there are some Pokemon I really, really want to use, but that's not too often. So yeah. It's basically just balancing out a team of Pokemon that I like and/or have wanted to use for a while.

Since I don't really do competitive battling, I base my choices off of most advantageous types toward gym leaders and the elite four + champions (most of the time that leaves bug, grass, poison, and ghost type pokemon off my list). I'm mainly offensive so I can just the sweep the NPC's pokemon.

Fire, electric, water/ice, rock/fighting/ground, psychic, and dark are my usual choices. That leaves out flying, dragon, normal, and steel.

honestly, i never put any thought in. if it's a pokemon that i like or it's cute, i'll take them and train them to be powerful.

In a casual playthrough

1)Must like the design - First and foremost. I'm not very picky when it comes to Pokemon, but for some reason I'm not into the usual...popular Pokemon. Their design bore me. Though they it's not limited to just them. I normally like the simplest designs (Pidgey, Krabby, Seaking, Pineco, Tauros, Surskit, Numel, Hippodown, etc) but I won't say no to creativity (Ludicolo, Hariyama, Dusclops, Tropius, Sharpedo, Trapinch family, Poliwhirl/Wrath, Farfetch'd, Dunsparce, Forretress, Croagunk etc) or plain goofy ones (Exeggutor, Weezing, Electrode, Garbodor, etc.)
2) Balance - What can this Pokemon do to my team? What support will it provide? Can it cover the others' weakness? Is their weakness a problem? Basically, it gotta provide a good balance. (But not necessarily.)
EDIT: I'd like to add that I don't plan my team ahead of the playthroughs. I assemble my team as the playthrough goes on. If I stumble across a Pokemon I'd like to use, I'll most likely will.

I don't battle competitively anymore but team building WAS my strength. Not anymore. I have a thread that includes my thought process while making a competitive team, so search my thread history for that. It's called Beauty in the Desert I believe.