I mostly (if not entirely) count on the review of french website jeuxvideo.com (french is my second language) and for a good reason; as their scores are 90% on par with my taste.
You can of course make same exception for some big names like COD (that still manage to get 17 or even 18 for black ops) and fifa witch gets at least 17.
Now an 18 for this site is very very good, it goes like this:
Anything under 8-7 hilariously bad. They even make review videos sometimes to make fun of them.
11-10-9 very bad
12-14 bad-not a fun experience
15 good
16-17 very good
18 excellent
19 (highest number) masterpiece
20 The legend of Zelda Wind Waker

I have tried using IGN but i found very unreliable and unconsistant (an 8 is not really that big of a deal).

Otherwise i like to hear the opinion of youtube reviewers like TotalBiscuit and angryjoe. feel free to suggest any site or youtube channel you think is great.

By the way Destiny got a 15 and i read the pro and con list and it is exactly what peaple have been saying in these forums.

I see a lot of people who pre ordered destiny dont believe in review scores anymore

I only really take this stance. 6 and below, maybe don't bother. 6 up, try it. Even 9/10 games sometimes I don't enjoy. But there are some 7/10s that are great fun just lack depth which is why they scored low.

I try to ignore the numbers and read the review and judge my own number. Also when you find reviewers that share similar tastes in games as you, you should put more weight into their reviews rather than say, random newsblogs

If the score is X/10, read it as (X-5)/5.

You shouldn't do math

Sometime of the best games get 6 or 7. 8 or 9 could be anywhere from mediocre to great and if 10/10 it only tells you that the reviewers been paid.

If it's your type of game, anything 5+ is worth considering.

I tend to ignore professional reviews as they're generally very uninformed. Look at the huge cult following games like Dynasty Warriors have, yet they rarely score anything above 6, yet if you talk to Dynasty Warriors fans, they'll sing most of the games praises viewing them as 9/10 games. Videogame journalism will never portrait that.

I try very hard to find reviews like Blistered Thumbs used to do, which gave you a score, but also a recommendation of, "Avoid," "For Fans Only," "Try it Out," or "Buy it Now." This freed up the reviewers to give the score they felt best without worrying too much about encapsulating the game into just that number.

Alas, BT is now defunct.

I usually read reviews looking for a few answers.

What gameplay can I expect? (I'll know if I will enjoy it just from hearing the outline).
Will the story be interesting? (Again, I'll know if I'll enjoy it from the blurb).
Does this reviewer share tastes with me? (Almost never happens).

If I spend more than 2-3 minutes reading at a review and can't answer at least two of those questions, it's a VERY BAD review.