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.
Step 4: The Shamrock
The following steps show a few typical mutants so you know what you are looking for.
The Classic 4-leaf clover has, well, 4 leaflets. Most mutants have three leaf stems in which one has split into two leaves, one usally smaller than the other. These types are probably produced by evironmental factors more than genetic factors (not that genes don't play a part). Clovers with 4 leaflets, evenly shaped, and 4 seperate leaflet stems are, from my experience, rarer, and probably strongly genetically influenced.
Note: There are a few companies that have tried to breed 4-leaf clovers to sell for their alleged lucky properties. Due to the complications between environmental and genetic influence, these breeds are tough to produce, and only marginally effective, or so i've read. heres one of these companies.
Step 5: 4 + N Clover
5, 6, 7, and so on -leaf clovers are rarer the more leaflets they have, but really stick out. Some have the attributes of several different kinds of mutants and can be really interesting.
Step 6: 3.5 Leaf Clovers, Color Variants, and "spades"
Some clovers (not very exciting, but pretty rare) have a mitten shaped leaflet due to conjoined leaves. You can tell they are conjoined by looking under the leaflet and noticing that it contains two stems (see below). Even rarer: sometimes part of conjoined leaf breaks off, with a little leaf sticking like a "thumb" off the mitten (sorry, no pic)
Some clovers will also have a "rust color". This is probably due to an inability of this clover to produce green chlorophyll in the leaflets, showing the less dominant red, yellow, or brown hues, much like how leaves turn colors in fall. Unlike deciduous plants, however, I've noticed this discoloration through out the year.
"Spade Leafed" clovers are a mystery to me. These clovers exhibit a strage shape of each leaf which reminds me of the shape of a spade. At first i thought it was due to insects, but the pattern is too perfect and insects too hungry to always produce this shape. Must be a mutant!(?) Weird...
Step 7: The Elusive 2-leaf Clover
O MY GOSH!! Just kidding, someones just messing with you. Though technically, its possible. Though tough to prove...
Step 8: Collecting and Displaying
I made a simple press to collect my clovers using two pieces of scrap wood and 4 machine screws with wing nuts at each corner. I placed duct tape on the inside of the press to make it easier to slide the note cards i used to seperate and label the clovers in and out. Sticking them in between two cards in your wallet works as well, but be prepared to have your credit card number etched into a leaf.
For mounting, I used a poster-sized picture frame (~$10) and the back of the promotional poster that came in it. I glued my dried, pressed clovers using a dab of elmers glue. Try to keep the mount as air tight as possible, as the clover's will loose their color over time.
Last summer i put this skill to the test: i found 166 4-leaf clovers, 11 5-leaf, and 2 3.5 leafs. After mounting these, i found one patch while mowing the lawn containing multiple 7 and 8 leaf clovers, as well as a 10 leaf.
All of the clovers pictured in this instructable were found in about 20 minutes of searching. They're out there, in many mutant combinations, so get looking and get lucky!