Always make contact with the solo ad vendor either by e-mail, Skype or Facebook.
Check the response time frame but of course take into consideration the time zone difference especially if they are based on the other side of the planet.
If a solo ad vendor takes more than 24 hours to respond, then the vendor is not keen to answer some basic questions. This attitude determines the service you will receive in 99% of the cases!
So here are 7 question you should always ask a solo ad vendor before purchasing a solo ad:
1) Do you have reviews from previous buyers?
2) When are you able to send out my e-mail swipe?
3) What percentage of Tier 1 countries can you offer me?
In most cases sales are made from one of the following 5 English speaking countries: UK, USA, Australia, New Zealand and Canada
4) When was the last time an email was sent regarding an offer similar to mine?
5) How many leads do you add to your list every single day and how do you replenish your list?
Having a huge list of subscribers does not mean quality! Smaller lists often outperform large publishers especially if the subscribers are presented with a number of freebies every single day!