The biggest thing when hiring an electrician (or any trade for that matter) is to be very specific about what you want, which may mean doing a little research yourself first, such as the site posted previously.
Never assume that the 'pro' you've hired knows it all, because the best ones know they don't, but will endevour to learn when necessary. If you only want to go with a 30A receptacle for your RV, be sure to specify your need for a "30A, 120V" supply. Even an apprentice should know that 120V means one hot, one neutral.
FWIW, i've been an electrician for 15 yrs or so. My dad has been an electrician for close to 40 yrs. While I have no problem with people wanting to do electrical themselves, please know when you're over you're head and get help. If nothing else, bring someone in to look at what you've done to verify it is correct. I know that myself, if everything looks good and there is no need to make changes, I won't even charge for the inspection.
Just my 2 cents, i'll get off my box now!