Consider these West hands after the following auction.
Should you bid further, hoping that game is possible, or should you pass, taking the view that since South has opening values game is unlikely? There is a good, simple rule of thumb available.
Decide the level to which you would have supported spades had you opened the bidding rather than doubling and then bid one less to allow for the fact that partner may have no HCP at all.
I.e. If you opened 1♥ and partner responded 1♠ if normally you would have rebid 2♠ you should now pass. If you intended to rebid 3♠ now bid 2♠.
If you intended to rebid 4♠ now bid 3♠.
b) 2♠, instead of 3♠
c) 3♠, instead of 4♠.