Well each person has their own unique way of RPing but there are a few basics things that each RP and RPer uses/has.
Step 1: Find a RP/Create Your Own RP
~ Find a RP that you are interested in becoming a part of. A RP, or Role Play, is a story that is acted out by many different people controlling their own unique characters. Each RP has one, or multiple, leaders (called GM(s)) that control the main flow of the story and that keep their RPers in line if some sort of conflict were to arise. The GM(s) are also the ones who set the rules and enforce them. They are basically the police of an RP. Each RP has a main story which the GM tries to keep to but lets the characters react to the situations, and to each other, in their own way. More advanced RPers can create their own RP and GM it if it gets approved by the Lead of the RP threads.
Step 2: Sign up/Character Creation
~ The next step is to check out the OOC (Out of Character) thread for that RP and find the SU (Sign Up) form for that RP. The SU is normally found within the OOC. Each RP has their own requirements for that particular RP but all of them normally require the following for your character:
*Name
*Age
*Gender
*Appearance
*Personality
*History
You will also find out more about that particular RP and a sneak peek about the story line in the OOC thread. Here is the OOC for one of the RPs I am currently in:
http://www.pokecommunity.com/showthread.php?t=266816
Step 3: Sign up
~Once creating your character and filling out the SU for the RP you must submit the SU (normally in the OOC thread) for approval by the GM. Once you are approved by the GM you are officially a part of the RP.
Step 4: Begin RPing
~ Once all the spots are filled the RP begins. Find either another RPer to work with or just jump right on in by merging your character into the surroundings that the GM sets up. At first it does take a little while to get the feel for the RP and your fellow RPers but once you get the hang of things it will flow smoothly. Here is the link to the actual RP for the OOC I posted higher up.
http://www.pokecommunity.com/showthread.php?t=268051
Long story short, you are telling/experiencing a story through a character you created and threw into that world. You are able to influence and change pieces of the story as long as you stay within the main flow of the story the GM sets up. :) The best way to get into RPing is to find a GM/RP that works well with beginning RPers and work with them to improve your RP skills. Also having a mentor can help. I'll be your mentor if you want to try your hand at RPing. If so, find a RP you want to try and contact the GM to see if they allow beginners and if they also allow mentors to help. :)