How often do chargebacks occur? Depends on how good u are at anti fraud & catching it, the more expierence you get the lower fraud rate you'll have, I for example automatically consider 10% of all sales as losses in terms of disputes/chargebacks.
How easy are they to dispute?
Non-receipt disputes require proof of delivery, so make sure u have that.
Unauthorized disputes u need things like ID,card etc to prove it was them making the purchase.
Unauthorized chargebacks u need ID,card, proof of delivery, and every bit of evidence u can get, highly unlikely ull win(I'd say 9/10 u lose), but every blue moon u might win one, automatically charges you a $20 chargeback fee win or lose, so really u lose either way with credit card unauthorized chargebacks.
What measures to I take to ensure I do not get chargebacked on?
I cant leak what I personally do, but most people would say setup a system such as receipt at x level, id at x level, card at x level, and limit card sales as much as possible without actually stinting sales/growth.
Compare their names on pp to their ID's, see how they act when u ask for ID, just get a general feel for them.
There's a very very basic anti fraud 101 for you that took me ~5 mins.