Leveling Steps

Step 1: Roll your HP Increase
Roll the HP die as determined by your Class and add your Constitution modifier, along with any potential miscellaneous bonuses from Feats or Species Traits. Add this final value to your Total HP. The character always gets at least 1 Hit Point with each new level, regardless of the player's die roll and the character's Constitution modifier.
Example: Lyrilis Vann, a Jedi, rolls 1d10 for a value of 9. She has a Constitution modifier of +2, so her total HP increases by 11.
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Step 2: Increase your Base Attack Bonus
Your Base Attack Bonus increases differently for each Class. Jedi and Soldier characters have a BAB equal to their Class Level; all other Classes have a BAB equal to three-quarters their class level, rounded down.
Example: Giarick Maylwar, a Noble, goes from level 5 to level 6, and his BAB increases from +3 to +4.
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Step 3: Increase your Defenses
All Defenses will increase by 1 each time you level up. Class bonuses to Defenses never change.
Example: C3-5AR, a Soldier, is a level 3 player character with Reflex, Fortitude, and Will Defense scores of 19, 15, and 12, respectively. When he levels up, his Reflex, Fortitude, and Will Defenses will be 20, 16, and 13.
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Step 4: Increase your Skill Bonuses
All Skills have a bonus equal to one half of your Character Level rounded down. This means your Skills will increase by +1 each time you reach an even Character Level.
Example: Salak, a Scout, is a level 5 character with a Stealth skill bonus of +11. When he reaches level 6, his Stealth skill bonus is +12.
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Step 5: Feats and Talents
Among other things, it can be difficult to understand when it is the right time to select Feats and Talents. Below are the bulleted instances to remember. The GM will help you through the process as well. 

• When your Class Level is even you may select a Bonus Feat, a limited list of Feats specific to your Class.
• When your Class Level is odd you may select a Talent that you meet all prerequisites for. Keep in mind that your Class, and occasionally your Species, determine which Talent Trees you have access to.
• Every third Character Level you may select any Feat which you meet the prerequisites for.

Example: Celes is a Shard and a Jedi who just reached level 3. She is eligible to take a Feat, as well as a Talent. She takes the Stand Tall feat and the Force Repair Talent from the Iron Knight Talent Tree (she can select this Talent because she is both a Shard and possesses the Force Sensitivity feat).
Example: Meena is a level 2 Scoundrel and is eligible to select a Bonus Feat. She can choose any option she qualifies for from the Bonus Feats (Scoundrel) page.
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Step 6: Ability Score Increases
Starting at your 4th Character Level, and every 4th level after that (i.e. 4th, 8th, 12th....), you will increase two Ability Scores by +1. You may not increase a single Ability Score by +2 at a time.
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Multiclassing
As previously mentioned, you may take a level in an additional class when you level up. A level 3 Soldier who takes her 4th level in Noble is denoted as a Soldier 3/Noble 1 character. If you choose to do this, you gain the Class Skills, 1st level Talent, and one Starting Feat of your choosing, nothing more.
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Prestige Classes
Prestige Classes are advanced and powerful Classes that most characters have access to at their 8th Character Level, with the exceptions of Independent Droid, Force Disciple, Jedi Master and Sith Lord. They often have extensive prerequisites and are designed to further specialize your character. If a player wants to take a Prestige Class, it is a good idea to begin planning ahead early on in order to secure the prerequisites that are required for the given Prestige Class of their choice. Taking a Prestige Class is very similar to Multiclassing, but with more significant abilities.