Usually when I play beginners who are beyond falling for scholars and fools mate and can do the basic checkmates; I just play like I always do, making logical moves and just playing them as if they were any other opponent. I never underestimate them.
Usually, after a few moves or so, they will make a tactical or positional blunder. Basically, I just wait for them to commit Hara-Kiri (suicide), nothing more than that.
Launching a kingside/queenside attack is also quite effective as beginners will usually panic in the face of the oncoming pawns and will blunder in such positions, being unaware of the various defensive and counterattacking methods.
Beginners are also usually unaware of endgames any more complex than the basic checkmates so you could just keep simplifying into an endgame where you have an advantage which they are unaware of such as a protected passed pawn, superior Knight vs bad Bishop, Rook on the seventh/second etc.