# I do not recommend going after IM as your first niche; the majority of money in the internet marketing niche is made through email lists. You're not going to sell through a blog (though you could build a list, but again, I discourage you for now) unless you have a lot of experience with writing exceptionally good copy; you need to remember you're selling to other marketers, and they tend to be significantly smarter than people who want to buy for example, a book on dogs.
# There is no such thing as a niche that is too competitive. One of my three blogs is in the MP3 Player niche, a very competitive market. It happens to be my second highest earner. If a niche is competitive, that means people are without a doubt, making money in it. If anyone tells you a niche is too competitive, it's probably because they don't want you stealing what could be their money! A less competitive niche is easier to conquer (obviously), but there is ALWAYS room in ANY niche.
# I do not sell digital products (though that is what I tried to do for several frustrating months). I sell physical products.
# Find a niche you're interested in. If you're interested in digital cameras, go for it. Passion is a more important factor than competitive-ness imo. I have a clothing site which has been limited due to me becoming really bored of the niche.
# Once you have a niche, the absolutely KEY thing to do is keyword research. This is where you get traffic.
http://freekeywords.wordtracker.com/ - use that to research keywords; you need to look for long-tail keywords that are several words long and target the ones which have low competitvity (this can be done using google, search allintitle:long tail keyword - lower search results means less competition)...
# Submit a few articles based on those long-tail keywords with links back to your blog (using another long tail keyword as the anchor text). That should get you going. Traget as many long-tails as you can...
That's all I can really give you... You need to come up with ways to generate long-term
backlinks using social networking sites, web2.0 sites, bookmarking sites, etc after you've done article submissions... just keep after long-tail keywords until you're getting decent traffic...
It took me 3 months before I got anywhere... Bare in mind it takes google a couple of months to begin taking your site seriously... you need to be working through that hard initial period... so many people do not even make it past that stage...