A suicide is a move that I view as the borderline between beginners and intermediate players. It is very versitile, rewarding, and most importantly, fun move that will possibly help you enjoy yo-yoing even more.
There are plenty of reasons that suicides are hard to learn, but here is some information and a tip that will make practicing them more enjoyable.
Keeping the string aligned is a maxim for most all yo-yo tricks that do not involve rejections, magic drops, or the like. (see the picture-in-picture about half-way through)
As a side note, your rhythm or pace will make a difference in the quality and ease of your suicides (especially the double suicide shown first!). Find the speed that is right for you.
Now get moving through the Instructable, watch the video a few times, and practice once you are finished.
And HA! I used a terribly hard-to-do voiceover.
Step 1: Trapeze
The yo-yo will land on the string supported by your free hand.
C'mon, you should know this.
A real suicide starts here, but there is a little change you can make to this mount to make the trick easier to learn.
That change is to use TWO FINGERS in the loop to start the suicide, like shown at the end of the video.
What this does is expand the loop that you must put your finger in BEFORE it comes around your throwhand. It essentially makes a bigger target for your finger to hit later.
Step 2: Under
The yo-yo stays on the string and swings under the hand that threw the yo-yo. The strings will be a bit bunched up here. It is important to keep the strings aligned.
Step 3: Release!
This is really one of the hardest parts to "get". All that is happening is that the finger (fingers, if you are using the tip) that is in the loop is being removed.
But it has to go somewhere, and it can not just magically re-position itself.
It is easiest to curl the finger(s) towards the body, almost like it (they) pivots towards the throwhand. This keeps the strings aligned and ready to open up once the yo-yo goes around.
Step 4: Open (sesame)
This is not really a step the player does. It happens if everything was done correctly up to this step.
If the strings are aligned, the spin of the yo-yo will force the response system to grip the string that is around the axle (the loop where the yo-yo is connected to the string), and move it so that the loop widens.
You can start tracking the loop at this step, and determine where it will be at it's widest point, so you can stick your finger in it.
This step is one of the hardest to have happen. Everything must be working together to do this.
Get your free hand ready, and...
Step 5: Catch
Once the yo-yo has come all the way around, you are now able to catch the loop again.
This step is hard to capture, and is really, really hard to do when you are learning the trick.
When you are starting the trick out, you may pinch with your thumb and forefinger. You will be cheating, but it's good for your ego while you practice.
Once your swing and release are doing well, you can start catching the loop.
Note: There are some free hand positions that are also considered unclassy, even if you did catch the loop. Make sure your palm faces inward (where it started, and where it hangs naturally). Now take a bow.