There are many variations of the card game "500" depending on where it is played and how many players there are, but usually players make rule improvements about the playing of the joker with no trumps, changing the bidding process, Misere contracts scoring and overall scoring. One way to improve the bidding rules is to allow people to bid after they have passed their turn or to allow the contractor to raise the bid and name a higher contract.
One rule improvement is to forbid players from nominating the joker to belong to a specific suit in advance or from playing it on a lead of a diamond. Some players don't allow a player to lead the joker until the last trick. Another way to play "500" is to use the joker as the first or last card of any suit.
As for Misere contracts, it is possible to let players bid a Misere before anyone has bid several tricks or to allow a player to bid Open Misere only after one of the players has bid eight or more tricks. Players may not allow Misere bids at all. Some players rank Misere bids between the eight of spades and eight of clubs.
One version of scoring rules is when a player's score reaches 490, he doesn't score points for tricks against contractors, and his score remains at 490 until he bids again. Some players don't count the ten points for each trick if the team has over 400 points.