I usually look for offers in countries with decent volume, and also tend to completely avoid certain verticals like Travels and Pay Per Call.
Other than that, I recently decided to skip gaming and casual dating offers because they don't seem to last more than a couple of months.
What about you ?
Something similar like you.
I also try to find out how exactly the conversion takes place. Some offers are marketed to affiliates as having an easy conversion flow.
But often all this stuff takes too long for me to find out and i just hit offers with some traffic, see what it does and go from there.
I like to move quick because often it just isn't worth it to spend so much time researching, tweaking, optimizing and then see the offer reaching it's monthly cap or being pulled completely.
Sometimes even this fails. Like recently: quick burst of traffic, optimize campaign, want to blast it with traffic and ask for a cap lift only to be informed the offer is going to be paused within 24 hrs. I should only do this at the start of the month :/
I find out the best converting offers at the time, and i look for a few things.
1. Is it in a country that has a lot of volume potential (not a lot of restrictions either)
or
2. Is it in a country with a lack of competition
3. Does it look like it'll be alive and kicking for atleast a few months
4. Then more personal things like does the landing page look good for how i usually run things, etc...
THEN I TEST!