Being a mate is extremely tough in terms of long hours. Poor base pay and sometimes you deal with A-holes the whole trip. You need to be able to be
a people person, cordial and interestng towards them. A good mate will keep the charter engaged in terms of the fishing and what is going on and also passing time via talking. You also need a lot of patience which hasn't been discussed. Some charters don't and wont listen to your suggestions, beat the hell out of the gear, and expect to be catered to. You also need on the water experience so that you can be able to respond to certain situations.
A great mate has a depth of knowledge of fishing techniques, knots, and being able to adjust and alter spreads. He or she will have an innate ability to untangle the mother of all tangles (sometimes with a knife)
and be able to multi-task (re-baiting, settting gear, explaining to the charter what is up, setting the hook, gaffing fish, etc all in short order) knowing that your tip will be decided sometimes by this.
I know many "PROFESSIONAL" mates on some of the best boats in the world and have the priviledge to fish with them a lot and they love what they do for a sure. But they are not getting rich, and some have other jobs to support their families.
Think about it. Also with the current economic state, gas/diesel prices, and the dollar not being what it was once worth, people losing jobs, I wouldn't be surprised to see some charter captains go out of business because the cost of doing business is too high for the average guy to pay for a day on the water. Ask some of the charter captains. I know of three captains who are getting "real" jobs in their eyes not mine, and are going to run trips only on weekends. They have bills on land as well as the sea to cover.
Lastly I dont know how much experience you have on a boat maybe a lot but if you dont have a lot of experience try to get on some peoples boats(personal) that you know to hone your skills.
Good luck, Matt