and the correct size sharp needle is a must, if your machine says use a 90/16(just a number, check the size recommended for what you are sewing) needle do so and make it a 'sharp' not a universal. and if using paper-back fusable, two that aren't too bad for sewing through are 'heat and bond lite' and wonderunder (a pellon product)
I have tried many different types and some work great the first time, then i use them on something else and it's next to impossible to sew through.