Some more serious suggestions:
-If you're not using rare candies for leveling up, always train in areas that pose 0 threat to your Pokémon, even if it takes time. It always hurts to lose Pokémon while training.
-Crits kill more Pokémon than you'd think, so plan around them by making sure your Pokémon won't die even if the opponent crits.
-Take advantage of dupes clause by looking at what Pokémon you can get in what route before heading in. You can always use repels to skip a route momentarily and then come back late.
-Don't be afraid to sacrifice Pokémon if needed. Sometimes it's better to intentionally have one mon die so others can survive than to have that Pokémon survive at the cost of all others. Pokémon with self-destruct/explosion can be pretty useful.
-Pokémon with immunities are extremely valuable if you're playing on set mode, so make sure you use Pokémon with Levitate, Storm Drain, Flash Fire, etc.
Now, some sillier ones:
-Do not, and I repeat, do NOT mess with Koffings, Wheezings, Electrodes and the likes. Those dudes killed my Pokémon way too much with exploding moves.
-Using good, strong Pokémon is cool and all, but if you're not playing a Hardcore Nuzlocke or something of higher difficulty, always have that one Pokémon that isn't really that useful but you just want to keep it around anyways. Usually that Pokémon is your starter, because, really, you don't need to keep it on you all the time y'know.
-Have fun. Nah really. If the average nuzlocke isn't fun to you, you can change the rules to be harder or easier, like with Monotype Nuzlockes and Hardcore Nuzlockes (my personal favorite) for higher difficulty, or... Whatever kind of nuzlocke is easier than the average nuzlocke. I'm sure you can make one up, though I haven't seen many out there.
I believe nuzlockes are pretty much for everyone who has played Pokémon more than once, so as long as you're looking at the bigger picture instead of being too fixated on specifics deaths, you'll most likely have a blast.
