I think the key is to find the right type of event. You need to be strategic and fussy about where you spend your time and money.
Who normally buys your services? Where can you find them? If it is the marketing person at a financial services co, then you need to find a group that will bring them together etc.
I am marketing freelancer and I have a niche. The events which are aimed at the niche are the ones I have had the most success from.
Like hopping I found my local groups to be full of life coaches, beauticians etc who I knew probably couldn't afford my services and that might be the same for you?
If you are aiming at local businesses then I am guessing a Chamber event will have slightly larger orgs represented.
In terms of what to expect, again it depends on the meeting. Some local meetings (4BN, WIBN) have a structure which the person who is running it should tell you before you go. Others are less structured, you go, you circulate and hand out business cards.
I don't really enjoy it (does anyone!??!) but I try to focus on the idea of meeting new people. I personally have rarely found networking a waste of time, you usually meet someone/find out something.
I would also suggest you ensure your online networking presence is good on LinkedIn. The people you meet might be checking you out & connecting etc.
Not sure I have given you the answer you were looking for, but my thoughts!