When purchasing bed sheets, what is the best Thread Count to purchase & the worst?

Many people enjoy high counts such as 400+ however, they may feel soft for a while, they wear faster. Anything less than 200 though, feels cheap and not always as soft. try 250-300 for a medium feel. Sometimes companies put a softener in the fabric that washes out. Buy a pillow case or something small, take it home and wash it to see if you still like it after that. This also works for towels.