Hi there and welcome to ECF! I too was a 30+yr smoker who made the transition almost a year ago ~ I haven't looked back!
Running Wolf gave some excellent advice above. I too suggest that you skip the slim style ecig type and opt for the mid range. As was mentioned above, there are different threaded devices (510, 808, 901, etc). I think the most common threads would be the 510, meaning, most parts/add-ons are designed to fit a 510 threaded device.
When choosing a starter kit, opt for one that offers at least 2 batteries (you'll need one to use while the other charges). Good starter kits should include a charger (ubc & wall adaptor), 2 batteries, and either cartomizers OR atomizers with cartridges. Some starter kits will come with pre-filled cartomizers or cartridges while others include blanks that will need to be filled with eliquid prior to use.
When buying eliquids you will need choose a flavour (any flavour you can possibly imagine is probably available, somewhere) and a nicotine strength. Nicotine is offered in terms of mg per mil and typically comes premixed in 0, 6, 12, 18, 24 and 36mg. Most folks start off trying the mid-range (18mg/ml) and from there, determine whether or not they may need to go higher or lower. To give you an idea, I was a pad smoker who used a 'light' cigarette brand. I found that 18mg was a bit too harsh for me and quickly settled in to using 12mg/ml. Heavy, 'full flavour', smokers find that 24mg/ml is more their speed.
If you have any questions, please ask away. We're all here to help!