This is difficult as you have 16 HCPs and your partner has not bid. You are vulnerable so you should probably PASS.
You have 10 HCPs and cannot bid 2H over 2C (as you would be promising 5 cards), so you should DBL promising both majors, even though you only have 3 cards in spades.
You have 18 HCPs but your partner has not responded to your 1C bid so must have 5 or less HCPs. Bid 1NT