What I learned from my first year as a dance mom:

1. Do not register for the 9am class on Saturday with your preschooler. She doesn't want to wake up on the weekend and neither do you
2. Do bring coffee with you to class; your dancer will have lots of energy when she gets out of class.
3. Tights will snag. So why not put on the ones that you noticed have a tiny snag right as you need to run out the door? Just say it happened in the car.
4. Talking to the other Dance Mom can be wonderful. This depends on what type of studio you are at though. If you went with the best (our friend is a teacher there), this will mean that there are mom's with designer jeans and full face of makeup and a iPad for the younger sibling to play with in the waiting room with you. Look for the mom with the frizzy hair or worn out sneakers, she will be cool..
5. Carefully consider any outing after class. She will be in her dance attire and she will not want to take it off. This means a trip to the mall with a fuzzy green unitard, baby pink tights with roses and nothing else (as it is freezing outside). You will get looks! You will want to kill people giving your child looks.
6. Tap shoes suck for little girls' feet. 
7. The hair must be up and detangler spray the night before and morning off is key. Brushing the hair before bed became a regular thing in our house after dance started. Tangles are the enemy!
8. Breakfast before the 9am class can be a half banana or 5 animal crackers. Oh, don't forget the juice box. (Did I mention that 9am classes suck?)
9. Little girls love getting makeup on, but hate standing still. Encourage a spin or tap of the feet from time to time.
10. Pictures are a big deal and the first practice that you will have. Do not freak out over tiny things. Look at the big picture.
11. The dress rehearsal will come up faster than you think and you will realize that you still don't have any mascara.
12. Waterproof mascara is a must! (for mom, too)
13. Don't forget snacks!
14. Pee before the unitard goes on!
15. Be early for everything. You will need much more time than you think to get your dancer ready.
16. Let your husband/SO/other family members be busy elsewhere while doing the prep work.
17. Become friends with the wonderful lady at the front desk. She knows everything that is going on and you need to know her name. 
18. Take pictures. Even of the grumpy faces.
19. Don't forget the tickets!
20. Stop. Breath. Enjoy your tiny dancer.

Mine is the one in the middle with the serious hip action!

I'm not sure how much this will help anyone. But its what I learned. That and whitening toothpaste is great at getting scuffs out of tap shoes. Please note that I use the term her/she for two reasons: I have a daughter and most tiny dancers are little girl. If you have a little boy that wants to dance, now is the time. When they are little it is cuter for a boy to be in class and he will get the chance to check it out. There was a little boy in class with my daughter the first month. Then *poof* - he must have not liked the shoes!