DP said some of the main things are the basic things such as:-
Support the schools decisions, parents sometimes forget that the teachers are the professionals of learning.
Turning up for events like sports day, shows, parents evening etc
Paying for trips & dinners on time.
If there is a problem, talk direct to the teacher and not "in the playground" (to other parents)
Make sure they have the right PE kit and equipment all of the time.
Support reading at home, like the other poster said, even just one page, sign the reading record and advise of any struggles.
If you buy books for them, take them to book shop with you so that they can choose.
Don't be afraid to challenge if you're unhappy with something. If you don't get a resolution, go through the appropriate channels (first the class teacher, then deputy then head)
Remember your kid is incredibly precious to you, but the class teacher will have 30 of them. Whilst they'll do there best to make your child feel special, theyll be doing the same to another 29 and sometimes things may be forgotten or not deemed as important to them as it is to you.
Hope this helps 