This is typically where you'll spend the most money in maintaining relaxed hair, but it's worth investing in a trusted stylist for touch-ups and/or coloring. They're licensed for a reason. Too many women (and children and men) are walking around today with damaged hair that's the result of home treatments.
Find a stylist you trust. This may not be easy; you may have to try several salons and get recommendations before you find someone you're happy with. Once you find a professional and build a good relationship with her, she should be able to advise you whether a lye or no-lye relaxer is best for you, which cuts will most flatter your face and how to care for your hair on a daily basis.