Depends. Have you ever attempted a maximum on said lift before? (If not, why not?!)
What I'll generally do is set a short-term goal for myself; a new maximum I want to achieve on that day. If you have never maxed on the lift before you'll want to take shorter jumps in weight to accurately gauge your limit.
If you have maxed before and you already know your limit poundage, it becomes easier, as you know what you achieved before and what you intend to achieve on that day.
Form follows function.