If you have friends in management positions and are in need of work, you may be tempted to ask one for a hand during your time of need. This can be the best or the worst idea depending on how it's done. In some cases asking outright might be acceptable, while in others, a bit more finesse may be required.
Request a Reference
Instead of coming out and saying you need a job, request a reference from your manager friend. In most cases he will be happy to help, and your request also tells him that you need work. If he knows of an opening or can use your talent, you may get a request to interview with his company as a result. If not, he may be flattered by your request and want to write the best letter he can for you. He may even take an interest in your search and try to open doors for you if possible.
Ask for Help
Contact the managers you know professionally via email and announce your search in a polite and unassuming way. For example, mention that you are seeking a new position and ask for permission to send along a copy of your resume in case anything comes up. By using a mass email, you avoid putting anyone on the spot and causing awkward situations. By asking before sending your resume you provide anyone who does not wish to assist with a way out. Follow up every few weeks or so with the managers who responded to your request positively.
If you are out of work, your instinct may be to start asking favors of your acquaintances in hopes of finding a job quickly. Change your focus and try your best to help managers you know to solve their own problems or expand their own business. Use your industry expertise and contacts to put together meetings that benefit your acquaintances. If people see you trying to help -- or better yet, if your meetings result in positive outcomes for your friends, they may be more likely to help you in your search or give you a call when opportunities rise.
Mention to your acquaintances that you are investigating a new field and the possibilities it may hold for you. By doing so, you announce your candidacy for jobs in the industry without actually asking for consideration. Announcing your intent also gives you an excuse to meet with managers you may know and to network as much as possible under the guise of familiarization. When you constantly keep your name in the mix and at the top of minds, there is more chance you will be the one they call when an opening appears.