For pasture primping, the best thing to do with a mane is to put it in basic braids about one inch across. Keeps it tangle free, clean, and won't pull out a ton of hair if your horse catches something. Don't use rubber bands for pasture braids; use electrical tape. Trust me! It stays in forever (doesn't break during cold days) and doesn't pull the hair.
For tails, I love three tube tail bags. Solid 3 Tube Tail Bag - Sleazy Sleepwear for Horses
Keeps a tail wonderfully clean and neat. Always tie your tail bag two inches below the end of the tail bone.
I like to condition and shampoo manes and tails once every two weeks with Mane N' Tail. If it's too cold to do that, no worries. Apply MGT weekly (small amounts; it doesn't take much!) If you aren't an MGT person, there is some wonderful stuff at Walmart called Hair Food. It's an amazing substance.
Inbetween, leave your braided manes and tails alone. No touchy. Take down and push once a week at most. Once every two weeks it better. Hair grows best when not messed with too much!