Instructions
Increase your character's hit points by the required amount. Depending on the rules your Dungeon Master uses, you will either have to roll a specific die and add the resulting number to your current HP total, or you will add a predetermined amount to your total. Consult the Player's Handbook if you need to know exactly which die or how many HP to add for your specific character class. Don't forget to add your constitution modifier to your HP as well at each level-up.
Distribute new skill points. Your character gains a specific amount of skill points based on his class and intelligence modifier with each level. Distribute these skill points into your character's available skills as you see fit. Consult the PHB to see exactly how many skill points you get at each level.
Select new abilities, spells and feats. Each class in D&D has their own set of unique powers and feats to use in and out of combat. When your character gains a level you will usually need to select an additional power or two to add to your available abilities. Once again, consult the PHB for a list of powers unique to your specific class, as well as what level they become available.
Increase your stats. Your character gains an extra stat point at every fourth level. This point can be added to any of your main stats.