Disclaimer: I'm going to speak about 'premium' ad sales. That means more or less fortune 500+ companies. This is my area of expertise so I won't speak to other types of sales.

I work for an ad network and have seen sites around your size flounder trying to do direct sales. Granted, there are a few (ala 100layercake.com) that are extremely focused on a very profitable genre (in their case: weddings). However, you're much better off bridging the gap in the short term.

Sign up for an ad network.

Figure out what your audience is like. How old? Male/female? Tech savvy?

Then go out and find a 'premium' network to fit your demo. For example, I work for Giantrealm.com and we serve 12-34 yr old males (our sweet spot is 18-34). We focus on Gaming/Entertainment/Lifestyle. Your blog would be a ... lifestyle blog I guess? If you're struggling with categorization, try thinking how you would be described by TV Guide. Lame, I know.

I've seen tons of sites try to get off google and go straight to direct sales. 99% of the time they fail because they aren't big enough to be on advertisers' radar.

Google CPM's (cost per thousand ad impressions): About $1.00 on a good day.

'Remnant' CPM's: $1.50-2.00

'Premium' CPM's: $4.00-12.00 depending on the unit and setup.

note: these prices are AFTER the standard 50/50 split with your ad network.

Although direct sales will make you more money in the long term, you have a number of items going against you by selling direct:

First and foremost, most advertisers won't blink an eye unless you're over 1,000,000 US unique visitors (the unit most advertisers think in). You can check this by looking at the separate box called 'Unique Visitors' on the Google Analytics dashboard and then segmenting by US.

Second: Advertisers usually work with an ad agency who takes care of most of the buying. Ad agencies are usually staffed by 'junior' account execs which are 20-24 yr old females (sorry to stereotype) that generally don't browse the internet beyond Facebook. They usually have no idea that your site exists and like to buy things they understand. They definitely don't understand your site. They don't understand most of our sites. It's the problem we face with 'niche' content that doesn't focus around Twilight video reviews and Lindsay Lohan paparazzi shots.

Third: Ad Agencies rely on an antiquated tool called Comscore. Comscore is like a database of nearly every site online and how big they are. Unfortunately, they rely mostly (this is changing nowadays) on panel-based metrics, which means that they call people on the phone, ask them if they would like to take an 'internet survey,' and then have them install a plugin on their machine to do so. You can imagine that most of your viewers probably won't be up for this. Most of our sites show up at 1/10th of their size on comscore. For example Gameriot.com, a site I worked on for a year, showed 800k unique visitors in Google Analytics. It showed up as 30k, 80k, 450k, then didn't show up. These are 4 consecutive months. I would try to find a friend to see if you show up.

Fourth: Advertising is alot of work. If you want to enter the true 'ad industry, you need to get used to what are called RFP cycles. Advertisers send out things called 'RFP's (Requests for Proposals) every few weeks that require you to do a TON of work (build a powerpoint deck that sums up your 'pitch') and fill out an excel spreadsheet in terms of 'media dollars' which is a convoluted way of saying "convert all dollars into banners, break it out by page, then give me a bunch of free stuff because I'm an advertiser and everyone else does."

Fifth: Advertising is all about connections. There's a reason that most sales people are given salaries that are directly based on their number of contacts. If you don't know anyone, you're going to have a hard time getting meetings. There are rumors about people buying football tickets, strippers, etc... No comment.

Ad Networks will go out and sell your site 'directly' (good ones at least) and pitch custom plans that your audience wil be excited about. Granted, sometimes they sell a load of shit and everybody hates it, but the best sales people sell campaigns that the site loves so users write positively about the brand.

The Ad Network model is to 'rep' a site 50/50 until the site becomes big enough (traffic-wise) to sell direct. At that point, they will offer you large sums of money NOT to sell direct :)

You'll also have a great idea of what sells on your site, what ads do well (use their campaign monitoring tools to see which advertisers keep buying you and what the click through rates are), so you'll be educated once you do start buying direct :)

Finally, if read all that and REALLY don't want to sign up for an ad network, you might try signing up for Google Ad Manager (Google's free ad server) and dabbling in ad exchanges. They use real-time engines to allow advertisers to bid against each other on your inventory. You can see rates of $2-6 this way if your site is popular.

If you have any questions about what ad units you should run (728x90, 300x250), how you should pitch your site, how ad servers work, or which ad networks to reach out to, I'm happy to help. E-mail is in my profile.