Choice has given you some good professional tips. So good to hear you will give it a go.
My tips are only from what i've had done myself and from being taught a lot about the hands on from the lady who did mine. You will know whether they are good as the hairs should simply 'slide' out after being zapped. You should NOT feel any definite tugging or pulling or definite tweezing of the hairs. They will most probably use a tweezer to pull the hair out, but not actually tweezing or pulling on it like when you pluck your eyebrows, just to slide it out. If they are definitely pulling it out then it's a waste of time.
Once they have done an area in your first appointment, then roughly about the 2 week mark is a good time. Ask them what phase the hairs are in, growing or nongrowing. The lady who i know who performs this would get her clients in approx every 2 weeks. She had a few girls who had serious growth on the face/neck area, made worse by plucking or shaving. I don't recall how long she said it took her, but then again she was a fast worker and i know for sure she had them hair free in under 12 months. There may have been the odd stray which needed removing, but the final strays are not that obvious.
You should start seeing results after the first few goes. The hairs will grow back finer and softer. Whatever you do, do NOT pluck them inbetween appointments. If you are embarrased you can bleach or trim, but do not wax or tweeze.
Ask them whether they will do a trial patch, just so that you can see how they do it, what it feels like and whether the person performing the electrolysis is doing it right or simply tweezing the hairs. Some times they might put the electric current setting on way too low. It's better up a bit higher, more efficient and it works first go without them having to repeated zaps.
Years and years ago i had electrolysis and after 9 months there were zero results. That put me off, but i didn't know what to expect. When i gave it another go with the lady who i became friends with i was amazed how if done properly you are definitely hair free forever.
After care is also important. Tea tree oil is a great disinfectant and then applying aloe vera gel is calming and diminishes any redness. Do not wash the area with water same day, wait until the following morning as this can cause infection.
All the best and hope you go through with it as you wont regret it