Other commonly used conventions are Gerber and Blackwood conventions used to identify slam potential, both of which have a number of variations.
The basic Gerber and Blackwood systems have positive and negative aspects, and some players use both systems depending on the bidding so far in the contract.
A bid of 4C asks partner to respond based on the number of aces in responder's hand.
4D shows 0 or 4 aces
4H shows 1 ace
4S shows 2 aces
4NT shows 3 aces
Following the response, the 'asker' can bid 5C asking for kings, in which case the responses are as above but one level up, or can sign off in any other bid.
A bid of 4NT asks partner to respond based on the number of aces in responder's hand.
5C shows 0 or 4 aces
5D shows 1 ace
5H shows 2 aces
5S shows 3 aces
If the 'asker' continues with a bid of 5NT, any response will be at the 6 level and a commitment to small slam. This needs to be taken into account as a response of, for example, 6D showing only 1 King may commit a bid at the 7 level if clubs are the preferred suit. In a major, where the 'asker' is looking to see if a grand slam is possible, this may be less disadvantageous, as a response showing 2 aces will still allow a pass at 6H.
It can be seen therefore that in the simplistic way above, Gerber would seem to be the obvious choice however using Gerber prevents the partnership from using 'Splinter' bids and using 4C as inviting partner to bid game at 5C. If 'Splinter' bids are not used (or any other special 4C) then the partnershp should decide whether gerber is more likely to be beneficial than the number of times 4C is bid naturally.
One solution to the above is to use Gerber in all cases (again providing 4C is not used in any Splinter/Convention) UNLESS the club suit has been bid naturally in which case Blackwood can be used.
It is important that a partnership agrees the full details of any convention including all possible responses and follow-up bids. It is also necessary to consider competitive auctions where the Convention may have opponents 'interfering'.