You mention you already have an idea of what your niche will be. It would be useful to know if your niche is a horizontal niche (the service you provide ie. marketing consulting) or a vertical niche (your ideal target market i.e.. dentists).
If you know your vertical niche then it becomes easier. I would do the following:
1. Identify the needs of your ideal client.
2. Highlight all the benefits your consulting service offers and create a compelling offer with your ideal client in mind.
3. Find out where your ideal client can be found and promote that offer to your ideal client. Local trade shows are more effective than chamber meetings. If your offer is good I would even try cold calling using online directories or a targeted leaflet drop.
PS. I couldn’t agree more with Jason’s comment regarding networking groups (glad it’s not just me!). I tried several local networking groups to find new clients. It quickly became clear that nobody had any money and I found them full of people having awkward conversations in which each party tried to sell their services to the other disinterested party.