Trial more than one VA for the same job - determine an identical project or task that can be assigned to several different people...a single task that takes up a significant portion of your time...this would certainly depend on the type of operation you are running, but for an example we'll say your daily or weekly news publication or perhaps your media postings. Chances are, one or two of the the several VAs will fail miserably leaving you with 3 or 4 worth keeping around. Repeat this process of elimination until you're left with the one person that seems dependable over the medium to long term. This will be your go-to VA for a start.

Certainly there will be some cost involved, but your freedom is invaluable.
Make it clear that you are looking for a long term relationship - But wait a minute ...doesn't that conflict with the previous statement? Well no...because you can have a long-term relationship with several VAs as long as the terms of your agreement are in writing and satisfactory to both (all parties). So when you "trialing" your VAs let them know that you plan to stay connected and present your business relationship as a valuable resource; with benefits for the both of you.
Don’t just check the VA’s references, check the references …references - Obviously there are privacy issues involved, however ....most anyone who has a business has left some sort of impression on the Internet. Therefore if a VA gives you a reference from a business, you can certainly see what that reference has to say about the VA and you can go a step further to see what the search engines have to say about the reference as well! You will find a much better relationship with a VA that has a great deal of experience with successful businesses that operate similarly to yours.

Well according to my resources, that the one big mistake you don't want to make in outsourcing!
Every task you assign should have been completed in full that is from beginning to end ...by you ....at least once…and it is suggested dozens of times and you should have the step by step written instructions for how the task should be completed.
The more specialized your operations, the more critical this point will be.
In larger organizations it's called SOP (Standard Operating Procedures) and yes small business owners need SOPs too!
I'll get deeper into that in another issue!
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In summary, I've got lot's more tips for helping you to decide if you are ready for outsourcing ....and I have some great tools to help you operate alone until you get to the "outsourcing" phase of your business.
Just connect with me.