ERS is definitely a game rife with variations and house rules. Here are two variant rules I have not seen documented anywhere else that I always prefer to play with:
While there is certainly some charm to the classic slap-jack style of play, it can get difficult with more than two players. An alternate form of claiming is to have players toss out a face-down card on to the top of the pot. A face-down card signals that the thrower is executing a claim and any other cards that end up face-up below can change the validity of the claim. This refines the race element of the game where players try to bury legitimate claims before they can be collected without having hands and cards in a jumble around the pot. In fact - when playing with this variant - hands near or touching the part are strictly forbidden unless a claim card has been successfully thrown.
When picking up a claimed pot (topped with a face-down card) the player picks up the pot, flips it, and places it immediately on the bottom of his/her deck. The bottom card of the deck is then pulled out and thrown face-up (no need to flip) to start the next pot.
Once players are fully familar with the rules a bluffing variant can be played as well. In a bluffing variant claim cards can be thrown whether invalid or valid and the thrower can pick up the pot. Any player who thinks the claim was invalid can challenge. If a challenge is made the loser of the challenge must place down his/her deck and cut it in half offering a choice to the challenger of which half to take ownership of.
For the bluffing variant be sure that the hierarchy of potential claims in the current house rules is well-known to all players to avoid confusion. A sample hierarchy is below:
1) Doubles (top card and card immediately below match in rank - claimable by owner of top card)
2) Failed Flush (last four cards match in suit but top card fails to match suit - claimable by owner of last valid card in flush)
3) Failed Run (last three cards make a sequence but top card fails to follow sequence - claimable by owner of last valid card in sequence) [Sequences terminate w/o any possibly claim at top (king) and bottom (ace) and do not go around the corner]
4) Failed Contract (a standard face card contract is opened and not met - claimable by owner of face card) [Contracts can be claimed after their respective length but can be met anytime after the length if the contract owner does not claim - example, Joe plays a Jack opening a contract with Jen, Jen plays a Two and then before Joe claims follows with an Ace, if Joe claims now it will be a misclaim on Jen as the contract was met - though after the standard length)