A cue bid of opener's major suit shows 5+ of the other major plus 5+ of one of the minors.
Most people play that Michaels is bid only with a weak hand or a very strong hand, while others play it with no strength specifications. In Bridge World, July 2004, p. 36, #1 is an example of a strong Michaels Cue Bid, but ironically, neither pair in the bidding contest had any restrictions on strength.
If you play Weak-Strong, then with an in-between hand, just double or overcall. With this agreement, if the Michaels bidder's LHO shows some strength by bidding, then the Michaels bidder probably is weak. In that case, or if you play weak-only Michaels, the partner of the Michaels bidder raises strictly on number of trumps he holds. (Known as a Total Tricks bid).
If Michaels' LHO passes, then Michaels responder's bids on the 2 level are Total Tricks, but jumps are based on strength rather than being preemptive.
For example, after 1-2-Dbl-?? where 2 shows 5-5 majors or more, Michaels partner adds the length of his longer major to the 5 promised by the Michaels bidder and then bids that number of tricks. With 3 Hearts, for example, 3+5=8, so bid for 8 tricks (2). With 4 of a major, bid 3. With 5+, bid 4.
With unfavorable vulnerability, you may not want to make a Total Tricks bids with a bad hand.
When partner has bid Michaels over a major, showing the other major and one minor, responder, with equal length in the minors, can bid notrump to ask partner to bid his minor. Example: (1)-2-(P)-2N, (P)-3.
Don't Balance With Michaels:
In practice, Michaels is bid with a weak hand far more often than with a strong one. Consequently, most people use Michaels in the direct (not in the balancing) position. (See Balancing.)