It's recommended that you have at least 5 a day, and up to 15 max. I don't often use less than 10, and I've been losing average 2lbs a week.
The syns element is as much a part of SW as the free, superfree and healthy extra foods, so do make sure you have them. They stop you feeling deprived, which can lead to bingeing, and also make sure you're daily calorie intake isn't low enough for the body to slip into starvation mode.
Often, people find they have better losses when they eat all of their syns, as opposed to not using any. It can sometimes kickstart the body into losing again.
In terms of using them, incorporate them into meals if you don't want to have speciffic treats, i.e using butter or oil when cooking, or use them for stewed or cooked fruit.
Try to mix your syns up a bit, as with everything variety is good for you!
HTH X