Tips tricks and suggestions for testing A/B testing marketing campaigns

Does anyone else have sites that use A/B testing marketing tools like Maximiser or Monetate?
What are some of the standard processes you use for testing? Tips or tricks?
We switched from Maximiser to Monetate and the testing functionality is very different now and has been getting a little bit frustrating.

Not familiar with those tools, but do they have some interface to query for which A/B path the user is assigned or interface to specifically set the A or B path the user will be assigned (rather than random arbitrary assignment)? Usually it would be through cookies, an HTTP querystring parameter, HTTP request header, REST API or something like that.

In terms of automation, if you wrap that interface in a framework, the tests would be agnostic to the actual A/B test framework implementation, and your test framework internally handles the messy details (when switching frameworks, etc.), exposing to the tests a generic interface to manage the A/B testing.