You keep your turn until you do one of four things:
1. Pass to the other team, where your score is frozen at the current level.
2. Hit a whammy, where your score is returned to the level where your turn started.
3. Fail to come up with a word.
4. Have your word challenged by the opponent.
The purpose of the Whammy, like in PYL, is to keep you from being too greedy.
As far as letter distribution, you probably want two buckets of 17 chips in it. These came from a list I use for most common words available when playing
Lingo as seen in
Mike's Game Show Round:
Beginning Letters: A, B, C, D, F, G, H, L, M, R, S, S, T, T, W, Whammy
Ending Letters: D, D, E, E, E, H, L, N, R, S, S, S, S, T, T, Y, Whammy
Plus one die to determine the letters:
1-3+ letters
2-4+ letters
3-5+ letters
4-3 letters only
5-4 letters only
6-5 letters only