Equipment – do some practice runs, maybe with neighbors or whatever and make sure you’re ready! Do the FULL flow, from talking on the phone, meeting up to show portfolio, taking pictures onsite, processing photos, handing off to clients for review, modifying if necessary, and ordering prints (if that’s what you offer). You could do it with ordering a few 4"x6"s if you don’t want to spend a lot. Trust me, you’ll be better off if you do this excersize. This will also tell you if you need additional equipment and supplies. For example, I was on a job 600 miles away and suddenly realized that people were tripping on my sync cords and I had no tape. D’oh! Lesson learned!

On that note, make sure you have a nice portfolio to show off, both hard copy and online. Do you have a website? You’ll need a nice one.
Do you have a marketing plan? Consider who your clients will be, HS Seniors, Brides, family, etc. If your answer is "everything" then break it up into sections and build a business model for each section.
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