Do your homework on the company. Get a list of their current and former clients and call at least 10 of them (at least two of them that joined in the past 6 months).
Don't hire an individual. Make sure when you contract with an outsourced IT company that you have the following in place:
1. They must notify you prior to outsourcing any of their work to another party (subcontract the work to someone you may or may not approve of).
2. They provide background checks on their employees.
3. They have privacy and other policies which they follow that comply with GLBA, HIPPA, or Sarbanes-Oxley (if necessary for your industry)
4. They will provide you with audited financial statements on at least an annual basis (you don't want to trust your goodies to someone that is going under and my be "pushed" towards unscrupulous behavior when the going gets tough).
5. There is no "automatic" renewal of the contract. (you should review their service at least annually to ensure they are doing the right thing)
6. They provide you with a copy of their support practices. (how many privileges does each employee have? Do they each have separate logins so you can tell who was doing what, etc.)
7. What State (if in the USA) laws is the contract governed by. Make sure it's not a State which is highly favorable to the outsourcing company.
8. The company is to maintain an insurance/bond policy against it employee negligent or malicious actions that harm your company. The amount of the insurance or bond should be sufficient to cover your assets and your liabilities if data stolen from you led to a lawsuit against you or your company.
There is a lot more you can/should do. I would also have an attorney well-versed in contract law examine the contract to ensure it completely spells out the outsourcing company's responsibility and yours without favoring one party over the other.
Good luck!