Fico score

Since I was 19 years old I went from no credit history to a low credit history  and I never seen my Fico Score move out of the 500 range, I've had several credit union loans with excellent repayment history but never seen the three credit bureau rating move up to 600 or 700 range.  I've also been a victim of identity theft were I had to place a block on my credit bureau information.  So my question is how do I achieve a higher score with a low credit rating and no major credit cards and no car or home loans.