The first thing to understand about ‘nearest point of relief’ is that there are a variety of conditions and scenarios where the term comes into play. Some Rules, e.g. immovable obstructions (Rule 24-2), abnormal ground conditions (25-1), require you to drop within one club-length of the nearest point of relief with no penalty. Other Rules, e.g. unplayable ball (Rule 28), simply require you to drop a ball within a certain number of club-lengths under penalty, e.g. in the case of Rule 28c, within two club-lengths of where the ball lies.
Once you have determined your nearest point of relief you may then use any club to measure out the one or two club-length dropping area, but what about when you are determining your nearest point of relief?
In determining the ‘nearest point of relief’, you ‘should’ use the club with which you expect to play your next stroke. This is a recommendation, hence ‘should’ rather than ‘must’, and you cannot be penalised for failing to follow the recommendation. But be warned! If you try to push the boundaries by using another club with which you could not reasonably expect to play your next stroke, you run the risk of identifying a spot which is not actually your nearest point of relief. If you do this, you may, as a consequence, drop your ball in a wrong place and if you play from there, you will be penalised under the applicable Rule.
For example, say you find yourself 100 yards from the hole but standing in casual water; you are entitled to relief without penalty under Rule 25-1. What you need to do is imagine that the casual water is not there and select the club that you would normally hit from that position, e.g. a pitching wedge. That would be the correct club to use in order to accurately determine your nearest point of relief. You would then use that club to simulate the address position, direction of play and swing. The nearest point of relief would be the point nearest to where the ball lies that is not nearer the hole and where, if the ball was positioned there, there would no longer be any interference from the casual water as you play your stroke.
Perhaps the most important thing of all to stress is that nearest point of relief does not mean nicest point of relief! There is only ever one nearest point, and sometimes it may be less appealing than where your ball is currently lying. But you don’t get any choice as to where the nearest point of relief is, and sometimes in such circumstances you may be better off playing the ball as it lies (e.g. from a path rather than from the deep heather beside it).