Just to help you start the ball rolling, here's the Keepers League rules we've formulated in Solar Keepers League which in turn was partially based on the MTC Keepers League.
You need rules for drafting, trades, how many players to keep, etc. I wouldn't mind explaining some of the rules we've crafted in our league if you want.
Solar Keepers League Official Rules
Roster Size
1. Teams must have 12 players at all times.
Trades
1. Trade review will be approved by Commissioner.
1.a If a trade that was approved by the League Commissioner is found highly objectionable by at least 2 GMs, that trade will be made available for review by the whole league.
1.b If 3/4ths of the members vote to veto the trade, the initial trade that was approved will be reversed by the League Commissioner.
2. Trades allowed:
a. player/s for draft picks or
b. player/s for player/s + draft picks or
c. picks for draft picks or
d. players/s + picks for player/s + draft picks
Additional Notes.
e. Multiple team trade (3 or more teams) will be allowed.
f. Only trade of future draft picks for the next season are allowed. Trading draft picks two or more seasons ahead of time are not allowed.
3. If a team receives a package of players that make them exceed the maximum roster size, that team must drop player/s in order to reach the league mandated roster size.
4. If a team lets go of players that make them drop below the league mandated, they must add players to fill the roster.
5. Trading of free agent picks aren't allowed.
In-season Player Movement
Adding/Dropping of Players
1. Limited to 40 moves per season.
2. Disabled for teams eliminated from the playoffs and consolation rounds once the YAHOO FANTASY LEAGUE PLAYOFFS begin.
Off-season Player Movement
1. Five players will be dropped at the start of each season. Team GMs will submit their 7 players (Keep 7) from their last season's lineup to the Commissioner thru email and PM (Solarent). Deadline is the last day of September.
2. In the event a GM has 3 or more picks for the Annual Rookie Draft (acquired thru trades), he has to either:
a. drop additional players equivalent to the number of picks he has beyond 2 from his roster or
b. waive rights to any of his draft picks
3. No Team can start the year with more than 12 players. If a GM has no rookie picks he/she has to start the year with 10 players, if he/she has only 1 pick he/she will start the year with 11 players. The vacant roster spots will be filled up by free agents who weren't picked from the free agent draft.
4. Offseason fantasy trades will be allowed BEFORE (after we have submitted our Keepers) & AFTER the Annual Rookie Draft. Offseason fantasy trades will temporarily cease 1 week before the opening game of the NBA schedule, at this same time the league will technically begin its season in Yahoo!.
Rookie Draft
1. Two (2) round rookie draft (OFFLINE) will be held every Second Monday of October.
2. Players selected in the Rookie draft must only be incoming rookies of the NBA season.
3. For the first round, all non-playoff teams after the Regular Season will go through a weighted lottery system to determine the #1, #2 and #3 picks. The rest of the teams will draft according to the reverse order of finish in the Regular Season.
4. The second round of the draft will be based on the reverse order of finish in the regular season.
Free Agent Draft
1. A three (3) round Free agent draft (OFFLINE) will be held every second Monday of October.
2. Players selected in the Free Agent draft most NOT be incoming rookies of the NBA season.
3. The Free Agent Draft will be done using the modified snake order (1st-last-last, 2nd-2nd to the last-2nd to the last, etc). The order of the free agent draft will be based on the reverse order of finish from the previous season.
Membership
1. New members must present their qualifications (Yahoo Fantasy profile, etc) and entry will be voted upon by existing members.
2. Expansion. The number of teams joining must be even in number.
Note: An expansion draft will be held where players not kept by the existing teams will be used as basis for incoming teams' rosters. Each expansion team is allowed to take seven (7) dropped players. This will be held before the Rookie and Free Agent drafts.
Note 2: The draft position (both Free Agent and Rookie) by the expansion teams will be the fourth and fifth picks (6th and 7th, and so on if necessary).
3. Members must notify their decision to quit 1st day of September. No notification means decision to continue membership in the league.
4. Contraction. If in the event there are no new owners found to replace quitting GMs, the number of quitting teams must be even, just like expansion. The players will be distributed using a dispersal draft using the snake rules.
Note: If an odd number of teams quits and no owner is found to make the quitting teams even, the commissioner and or a tribunal will manage the team but no trades and/or free agent pick-ups will be allowed.