FOLLOWING THE PATTERN
Sometimes when scrolling the blade, being black will blend in with the pattern we are trying to cut. When this happens it is easy to stray from the line.
There are a couple of ways of handling this.
1) Print your patterns in red ink, or photocopy in red. This way there is lots of contrast between the blade and the pattern
2) Place a light on the side of the saw. This will cast a shadow on the blade.
The point where the blade and the shadow meet is where the blade intersects the pattern, This will act as an arrow and make it easier to guide your work.
3) Run a high liter over the lines so they stand out better
BLADE WONT CUT STRAIGHT
I am sure that you have tried cutting a piece of wood in a straight line only to be frustrated by the saw wanting to cut at an angle. I think this is the number one reason people give up on scrolling.
It is not you, nor is it your saw. It is the blade. Many blades are milled out of metal, this makes one side of the blade cut more aggressively than the other.
The best way to correct this is to buy better blades. I like to use precision ground tooth blades or PGT. It doesn't matter so much on the brand you use, as long as they are precision ground. These blades have the teeth sharpened and set like a regular saw.
If you cant get hold of PGT blades don’t worry. There is another way you can work around this problem. Cut a test piece of wood and note the direction of the cut. It will probably drift to the right a few degrees.
Shift your seating position in front of your saw. Don’t use the back of the saw as a reference point. The only thing you have to use as a reference point is the blade.
Once you have offset yourself, take a few more cuts and get a feel for the blade.