The World of Gymnastics is a great site that helped me compile some of this information. I encourage you to check out the site! Its author provides requirements for routines of various levels.
The USAG competitive program scores gymnasts out of a possible 10.0 in each event. Gymnasts are responsible for performing all the required skills within their routines for any given level. Each skill, then, has requirements of its own (i.e. - handstands must be held for a certain amount of time, split leaps must meet a degree requirement, bent legs and flexed feet will be deducted in a back handspring, etc.) Needless to say, keeping track of all the requirements and deductions is nearly impossible for gymnasts, parents, and sometimes even coaches, so I thought it would be helpful to compile all the main information into one place, beginning with the most important requirements for a level 5 floor routine.
The first thing to know is that the gymnast will be deducted for performing out of time with the music, stepping out of bounds, falling on a skill, or lacking fluidity. They will also be deducted slightly if their undergarments show from underneath their leotard. They will NOT be deducted for failing to smile, failing to make eye contact with the judges, etc., but many years of competitive gymnastics experience tells me that those things do make a big difference in overall appeal.
Straddle jump. Split must be at least 120 degrees. A .2 maximum deduction will be taken if the gymnast fails to straddle wide enough. Another .1 can be taken if the gymnast does not bring her feet back together upon landing. Judges will look for straight legs and pointed toes.
Dive roll. Gymnast must maintain a hollow body position (not arched, not piked). Up to .2 points will be taken for body position mistakes, and .2 will be taken if the gymnast does not show flight before her hands hit the floor. Judges will look to see that the gymnast springs off her toes and controls her landing. Hands cannot hit the floor more than once on this move. If the gymnast fails to control the landing and falls back onto her hands, .3 can be taken from her score.
Front handspring. Gymnast must block with her shoulders (for the parents out there, that means they have to "spring" off their hands with straight arms using a shoulder push, rather than bending their arms and pushing up that way). This is worth .2 points. If the gymnast fails to block at all and limbers over, .6 will be taken. A front limber is NOT the same thing as a front handspring, and the skill will be considered incomplete if a limber is performed in its place. Hands must land at the same time side-by-side, and the same goes for the feet. The gymnast must rebound immediately out of the handspring with arms tight by ears. Judges will look for nice tight body position with straight legs and pointed toes. The gymnast also must begin the skill with a hurdle.
Split leap. Leap must reach a minimum of a 120 degree leg separation. This is worth .2. Front leg bent on the take-off will be .1 deduction. Again, judges will look for tight, straight legs and pointed toes.
Split (on ground). Must be a full, 180 degree split. .2 deduction if the gymnast fails to sit all the way down in her split.
Back extension roll. Gymnast should not place hands on the floor before rolling backwards. This can be up to a .3 deduction. A backward roll to stand should not be substituted for the back extension roll. Much like with the handspring/limber situation, a backward roll in this case is considered an element change and will be a .6 deduction. Gymnast must pass through vertical (i.e. hit the handstand position) - a .3 deduction can be taken for failing to do this. Hands must be placed on the floor in unison. Gymnast should not bend arms and push up - this skill requires straight arms, opening the shoulder angle and pushing into the ground with the hands for the upwards momentum. Judges will look at body position in the vertical just like they would for a normal handstand (so arching, leg separation, head out, bent legs, and other similar mistakes will be worth a deduction).
Full turn. Gymnast must be in releve (high toe) with the other foot in coupe position at the ankle. Must turn a full 360 degrees. If the gymnast fails to do these things the deduction can be up to .4 points. Judges will look for a controlled landing.
Back walkover. Leg separation in the walkover must be at least 150 degrees. Failure to split to 150 will cause a deduction up to .2 depending on how far from the required angle the gymnast is. Hands must land in unison. Legs must continually kick over, so the gymnast should not let their front leg drop after lifting it as they go into the walkover.
Round off, two back handsprings. Judges will look for a big hurdle with this skill. The round off must pass through vertical (.3 deduction for failing to do so). Feet must land at the same time. Judges will look to see that the gymnast snaps the feet down and together, preparing for the back handspring. The gymnast should then continue into the back handspring with no hesitation. The gymnast should be in constant acceleration during this tumbling pass, which is worth .2. Gymnast must not squat too low or undercut the handsprings. Must rebound directly out of the 2nd handspring (worth .1). Judges will look for nice, stretched body position, straight legs with no separation, and a controlled landing.
These are the main skills and deductions to focus on. There are little things here and there that I didn't list - mostly dance elements like the hitch kick, the waltz step, and that type of thing. Hope this helps.