One of the best strategies in temping is simply to register with as many agencies as you can. The more agencies you're registered with, the more work offers you get, and the more offers, the easier it is to find a decent, well-paying assignment. And if it's done with respect, both the agency and the temp benefit.
The news reports are often full of politicians talking about the wonders of capitalism, and how competition benefits the economy. What encourages competition like nothing else? Comparison shopping! There are 171 temp agencies listed in the Yellow Pages, and many more that aren't. The client firms themselves almost always work with several agencies. The more offers you get, the more you'll have to choose from.
Another advantage is practice. Interviewing and testing are skills, and improve the more you do them. The more times you've taken the Excel for Windows Qwiz test, the faster you'll do, and the higher you'll score.
In addition, agencies experience cycles. A perfectly good agency may suddenly hit a dry spell. Perhaps they've just hired a new counselor who's not very well known with the client firms. You can insulate yourself from this by registering with several agencies.
That said, there is an advantage to having a regular agency. The agency, and eventually their clients, get to know you, and give you steady, decent work. But it often takes a while to find an agency you can develop that relationship with. If an agency regularly leaves you without work for weeks at a time, you should at least look for other agencies to fill that time.
I always feel a twinge of guilt at registering with more than one agency. In fact, I've even gone so far as to try and hide it, telling one agency I was out with friends when I was actually on standby at another agency. But I eventually realized that it wasn't a productive attitude. The agency-temp relationship isn't marriage. Each agency has hundreds, if not thousands, of temps. Why shouldn't you have a few agencies?
The key is to do it with respect and honesty. A good agency, in my experience, doesn't mind competing with another agency because they know they have good assignments. Each agency doesn't have to know the names of the others; they just have to know that there are others. Be sure to make arrangements for them to contact you; if you're out interviewing, testing or on standby, check your messages regularly, or check in with the agency. If you're out on assignment, let all your agencies know when you'll be available again. [an error occurred while processing this directive]