Lighten hair for summer
You are absolutely right to go to a salon to get your lightening done, they can do a good job and show you some swatches so you can pick the right color before you start. The trend that I really like for summer is an ombre look, where the ends are lighter than the roots in a gradual effect. This just looks so beachy and has the added benefit that you don't need color touch-ups as often since your darker roots sort of blend in with this look.
I'd go for the ombre look, but I don't recommend doing it yourself.
I used to do my own highlights, and that was fine. I got ballsy one day and decided to go blonde.... and I came out looking like Lady Gaga with banana yellow hair.
When it comes to lightening your hair, go to a salon and get it done.