If using an extension cord from shore power cord to house, use a decent heavy duty one with #14 ga. wire, unless it's a long run when #12 or better should be used.  
Be mindful of the voltage inside your RV if running anything inside other than small loads like fridge and converter as a long extension cord(s) can cause or worsen voltage drop.  A 120 volt power line monitor inside your RV is always a good thing to have regardless.
You should always turn the power off before plugging in your RV.  If you don't, you'll get pitting on the plug blades and inside a receptacle or connector, which eventually builds up resistance from poor contact resulting in a meltdown from overheating.  Turn power off at breaker in house or 30 amp main breaker in RV's panel.  I've had 2 cheap extension cords go up in smoke in the driveway from being too lazy to shut the power off.  (Now have a 30 amp dedicated RV recept. in carport complete with disconnect switch.)