When I've gone for a 1RM (I'll use my 190kg DL as an example), I've just done my usual warmup set of ~6x 100kg, then 3x 140kg, 3x 160kg (was my working weight at the time, normal rep range of 5-8), then the 1RM attemp (which I got 2 reps of ).
This wouldn't be a normal routine by any means, and I'm sure there's better ways to do it. It's just what I went with - warmup, then step up incrementally doing only a few reps at each weight, then 1RM