I find four-leaf clovers frequently, even when not explicitly looking. Many find this "gift" extraordinary, and even though this mutation is reported to only occur once in about 10,000 clovers, getting lucky isn't as hard as one would think.
Step 1: Background: The Clover
4-leaf clovers are a mutation of the usually 3-leafed White Clover plant, Trifolium repens. One clover is actually one leaf of a larger plant, with 3 leaflets. Mutations can occur due to a low frequency recessive gene or environmental causes. Often the reason for mutation is differentiable from one clover to another. The mutation does not stop at the 4-leafed variety: 5-leafed clovers are not uncommon. However, the more leaflets, the harder they are to find (and the luckier they are): the record is an 18-leaf clover, and the highest I've ever seen is 10-leafed.
Step 2: Patterns, Patterns, Patterns
First, find a large patch of Clover, which isn't hard to do if you have a lawn or live near a park.
Do not get on your hands and knees with magnifying glass in hand, individually examining each clover. From standing height, look over the entire patch, brushing the clover with your foot to ensure none remain unexposed. If you enjoy math problems, eye-spys, the game "SET", or any pattern game in general, you'll be in your element. Amongst all the sets of 3 leaflets, any mutation will stick out like a sore thumb.
Step 3: Statistically Speaking...
Remember, 78% of all statistics are made up. So even though they say there is only one 4-leafer in 10,000 clovers, thats not entirely the whole story. One clover is just a member of one White Clover plant, which can cover from a few square inches to a few square feet. And some plants are more susceptible to mutation than others, so if you find one, look hard in the near vicinity. Several of the mutants pictured in the following steps were all found within a few square inches.
Mutant clovers are also more prevalent later in summer than they are in spring, and some places just seem more environmentally favorable to produce mutants.