Most game players, or the ones I know, accept that once a phase is complete there's no going back to retrospectively do anything you previously should have thought about but didn't.
All but the very best, non-intoxicated - we usually get the beers out when we have a game :) - pros will forget some of the above on occassions.
Here, I'm going to give you some tips that will help you remember.
Army List of units and characters.
First off, make sure you create a summary army list before the game, you should have a list anyway unless you have a photographic memory !
Turn sequence (phase) list
Also, before battle begins create a sequence list showing all the phases in the game. At the top of each phase write any army wide special rules (eg. +1 dispel dice) Then under each phase write the special rules you might need to remember for each unit. For example, unit X has a magic banner +D6 inch charge for 1st charge of game.
After battlefield deployment but before any battle comences give each unit / character a number on your army list summary going from your left most unit to your rightmost unit / character. This will be the general order in which you move / fire etc with your units.
Now when battle begins simply check the phase list first for any army wide special rules and then check the unit number that you are about to deal with on the sequence list to jog your memory of any special rules or items you need to consider.
I hope that makes sense, if it doesn't please let me know and I'll include some photos of a sample army list and sequence list.
It might not win you any battles - although you never know ! What it will do is wipe out those feelings of frustration at having forgotten something important.
