After the opponents have opened at the one-level, the overcaller bids the same suit at the two-level; the two normal cases are: Partnerships who have incorporated Michaels cuebids amongst their agreements usually also play the unusual notrump convention.
With less than eight points, Michaels is not recommended - the chances of winning the auction are small and it gives the opponents too much information.
In the Netherlands, a particular modification is growing in popularity: over opponent's opening, a cuebid shows a major and a minor unbid suit.
Compared to standard Michaels, the disadvantage is that after an opposing minor suit opening, one cannot introduce a two suiter in the majors at the two-level.
Compared to standard Michaels, the disadvantage is that after an opposing minor suit opening, one cannot describe a two suiter in the majors in one bid.
Another two-suited overcall system defining both suits explicitly is CRO (Colour, Rank, Other) which has similar advantages and disadvantages to Ghestem.