Leave your hair alone! Try finger combing, that way you don't lose hair unnecessarily. If you need to detangle, use a wide tooth shower comb to do so, but finger detangle first! Opt for styles that require no heat i.e. buns, braid outs, twist outs etc. Give your hair a break and it will thank you for it.
Deep conditioning restores strength and elasticity making the strands more resilient. Strong hair equals less breakage, and less breakage equals length retention. Deep conditioning is best done with heat (heating cap, steamer, hooded dryer) for 20-30mins or 1hr without heat.
Reduce hair manipulation/combing by incorporating buns, braids, clipped up/updo's, weaves and wigs into your regimen. Keeping the ends protected from outside elements is essential for hair health and length retention. Wearing a satin/silk scarf prevents dryness in the hair.