All the rules of regular chess apply. However, players are restricted in their initial moves, in that they may only move pawns until one of the following things happens:
Once of those three things happens in a game, both players are released from the pawns only stricture, and may thereafter make whatever moves are allowed under the rules of the regular game. That includes castling, however inadvisable it might be in a game of this sort.
And of course if the stricture is lifted because a king is in check, the checked player is then obligated to get out of check, most likely by moving a queen, bishop or knight.
PLACEHOLDER
I have not played enough games of this variant to make any strategy suggestions.