Assuming you're selling via something like flippa:

You've been around less than a year? Figure on 1x proven revenue. If your AdSense earnings to date are $8,000, then the offer would be about $8,000. If you're lucky, someone might annualize it ($8k in 8 months -> $12k).

Why so little?

1) Your site is new. Shiny new things are risky: how much of the ongoing traffic is trendseekers who will be gone in two months? What is the odds of Google deciding to smack you down in the next 6 months? etc

2) You are currently valuing your time at zero. The purchaser of the site will likely own many websites and operate them as a business. He does not value his time at zero. People in our industry are expensive: it is highly likely that, if you take the imputed value of your salary out of those AdSense checks, the site is actually losing money every month. (You may, for whatever reason, undervalue your own fair market value. Your purchaser is likely to be savvier about it than you. By the way, if you can routinely get websites to 300k uniques per month, here's my most important piece of advice: $1.5k is not a large amount of money for you anymore.)

3) You have what you believe to be a reasonable expectation of continued growth. The purchaser of the website will not bank on continued growth: if it happens, it is his upside, but as he maintains a portfolio he will probably be unwilling to make this site his #1 priority. He also knows that many sure things can catch a bullet from Google two months down the line, quite possibly for something he has no control over.

4) Everybody says they're selling the site for personal reasons and everybody in the market assumes that this is code for "I believe that this site has peaked and want to maximize the amount I get for it prior to it entering into a period of decline or getting burned."

Now, in terms of mechanisms, most serious deals end up with the site getting placed into escrow -- you convey the domain name and assets (logins, whatever) to a trusted third party, purchaser pays trusted third party, trusted third party effects simultaneous transfer. My low-end valuation for you would put you close to the point where some people might do a deal without escrow.

Factors which could make a difference:

1) Finding an individual buyer who saw strategic value in the website. Like, hypothetically if you were Crossword Puzzle Creator and I decided to buy you, you're more valuable to me than to Random Affiliate Marketer #302 because I have obvious cross-promotion opportunities with my existing business.

2) Things which make your traffic or revenue stickier than it would otherwise be. (You'd get much more money if you had $1,500 a month in rebill income from subscribers or from people buying upgrades in an online RPG, etc.)

3) Factors which tend to make your traffic more valuable than the value you are extracting from it currently. (If you were generally getting people through organic Google searches with high commercial intent, for example, substandard monetization at present might not be a barrier to a dedicated purchaser who thought to immediately rip out your monetization and then do it properly.)

4) You demonstrate higher than average salesmanship ability in identifying and then selling a particular prospect on the value of this site, as opposed to going to a marketplace like flippa.