I recently took a class at our guild on quilting/FMQing. In preparation for the class we had to make 12 13" quilt sandwiches out of muslin, then draw a 1" grid on each one with a washable pen....not the air-disappearing one. A couple of the grids were 60 degree diamonds which can be done with any ruler that has that angle on it. These were our practice pieces and they are now wonderful reference pieces.
The concept is that you think in squares and with only a little practice you can go freely from one square to the next. Whatever design you create......squiggles, flowers, leaves, vines, arcs, stippling.....just keep going from one square to the next in whatever space you want to quilt in. Starting with small squares makes it easy to see & create designs, and they can then be easily enlarged to fit larger spaces.
Other than that....practice, PATIENCE, deep breaths, RELAX THE HANDS AND SHOULDERS, sharp needle, gloves (I like the white Machingers because they're lightweight), and more patience.....just do it!
Also....if your machine has an "auto-pilot" feature where you unplug your foot pedal and push a start/stop button to stitch.....try using this feature on a practice piece. I find when I use it my stitches are MUCH more even, I relax my hands more and the overall look is more professional....the photo below shows my first meandering using the auto-pilot.
Good luck and have fun with it!! Karen