The image above is a photo of the string of beads I usually use. It's made of 99 wooden beads. I wasn't too concerned about the type of wood when I made it several year ago, it might be an olive of some sort.
I chose the number 99 for a few reasons. First, at the time I made it, I was very taken with the idea of the 99 Most Beautiful Names of God in the Qur'an. I'd tried to memorize them, but gave up when I got into the 20's or so.
Second, it seemed to be the number that spanned several traditions and that appealed to me. As I learned more about it, that notion fell apart. Numbers turned out to be more diverse than I'd through (for more information, see the reference links page):
Buddhist - 27, 108, 111
Christian (Anglican) - 33 (divisor of 99!)
Christian (Roman Catholic) - Chaplets of 15, 39, 42, 12 and various other numbers (I grew up with the Catholic Rosary. There are 5 'decades' or groups of 10, a group of 3 and an additional 6 beads that are used to group the decades. So the total number is not really significant.)
Hindu - 108
Islam - 99
Sikh - 108 (or 99 knots on a prayer string)
Taoist - 108
The third reason is a bit less esoteric: it was a good size for wrapping around my wrist 4 times. The first time I saw someone wearing (as opposed to using) them, I asked her about it and it was a 99 bead piece. So, a little nod to my personal history.
Using the Beads
I've been using the beads (on and off) since the early 1990's. My use evolved over the years and there are now three main ways I use them:
repetition/meditation - this is probably the most well-known use of prayer beads. Some traditions prescribe a phrase, prayer, or prayers to be repeated as you finger your way through the beads. I've used the Catholic rosary sequence, repetition of the Jesus Prayer (references here and here), and repetition of short scripture passages (a spin on the lectio divina concept).
contemplation - the word contemplation is often linked with the word meditation but I'm using it in a more secular way: the idea of thinking something through, mulling it over, contemplating it. I discovered this style when I stopped fighting the free association that sometimes goes on while praying (it does for me at least!). I'd find myself distracted by something that happened during the day or some stress that loomed large on my mind. So, I "went with is". And found that it was often very beneficial. So, if you want to try this, here's what you do:
Pick a short phrase (keep it short) that captures what's distracting you (like "What to do about my job?" or "I sure handled that badly!".
Repeate it over and over, once for each bead. Stay loose and responsive to what happens.
Often, the phrase will morph into something similar but slightly different like "It's not the job, it's the schedule." or "I could have handled that better.").
Keep going with it until you hit a point where it feels like you're no longer driving the changes in The phrase, but it's changing on its own.
At this point, you will either start feeling better or realize that you're not going to get past whatever is bothering you in a single session. Take a break and try tomorrow.
Note that this may not lead to a solution to your situation. In fact, it often doesn't. But I've found pretty consistently that it gives you some distance and perspective. And that helps a lot.
gratefulness - can you come up with 33 (or 99?) things that happened to you today that you are thankful for? That's the core of this approach. I typically start with bead 1 being something like "I'm thankful I woke up this morning", bead 2 is "I'm glad that my allergies are not acting up this morning", etc. through the entire 33.
Ever since meeting Brother David Steindl-Rast and reading his book Gratefulness, the Heart of Prayer, I've tried to remind myself that saying "thank you" is a completely legitimate function of prayer. What better way to interact with God, really? I'm not much for "hey, God, could you find me a better job?" or "please help me get over the flu", but I do understand the idea of saying "thanks for the wonderful life you've dropped me in the middle of".
You might want to try one or more of these techniques, see what kind of reuslts you get.