Let's face it hair extensions are expensive so here are some tips to keep them in the best condition
use sulfate FREE shampoo & conditioner
apply hair oil on mids to ends every day
brush hair a couple of times a day to prevent tangling
blow dry the weft part before going to bed to prevent itchiness & tangle
wear hair in loose braid or bun to sleep
sleep with silk or satin pillow case or a silk bonnet
if you're going to swim, put conditioner on your hair and put in a loose braid. However, pools have a lot of strong chemicals that are not good for the hair so I would recommend not getting extensions wet.
Make sure to brush your extensions from bottom to top and throughly to ensure no knots form!