Some basic tips for cosplay include:
Practicing poses in front of the mirror before a convention. When people ask you for a picture, you want to have a dynamic, in-character pose for them!
Bring some snacks/water with you during the convention. Being hydrated is very important! Bring things like a sewing kit, hot glue gun, safety pins in case any cosplay malfunctions occur. Also make sure your cell phone/cameras are all charged before you go to the con!
Those are just some very general tips, if you want more detailed advice, there are sub-forums with a wide variety of topics (wigs, make-up, prop construction, photography) that will prove helpful. Good luck!