Solo ads - how to choose the best list

What do you think is the best way to select a solo ad service? There are so many different lists out there and they vary in price - it's hard to make a decision when most of the time all you have to go on is an ad with a few testimonials.
Here is some advise that was recommended to me on another forum:

• Your offer-to-list match: is your offer a good match for the list's target market
• How credible the ezine/newsletter owner or solo ad mailer is
• How often does he or she mail: not too much; not too little
• Open rate history: are people even opening and reading the emails
• How many subscribers: big lists are great, but they don't always mean they're good

How is it possible to check this information? How can I check what people claim is true about the quality of their list?

I reckon the only way is to throw money at 100 clicks and see what sticks.

Also, who thinks it's important it is to switch things up by using different lists?

Do you think Is it important to continuously source new solo ad lists? Or is it a case of if it aint broke, dont fix it?
Gimme your oppinion but please dont pm me with offers for paid solo ads

Its all about trial and error... throw out a 100 click and track the traffic..what have the highest duration time, whats making sales.. and go from there.. what ever works you invest more into it.

I think it is ok to source other lists, but at the same time, it is ok to stick with a particular list for a stretch of time if the list is constantly growing.