For instance, let's say you have a game blog. Do you target one or two main keywords for the entire blog and then some long tail keywords for each post. Or, do you pick different keywords (within your niche) to target for each post? What's your technique?
I also owns a game blog that is known as gamingadda99.blogspot.com. I am using the different keywords related to the each post that i have but with the concept of having the two or three main keywords with the additions tags as keywords which is just exact to the post name. this technique is going good for me.
Are you using these keywords to backlink to your site? Since the Penguin update, there is some indication that backlinking using the same keywords over numerous links is a bad thing and perceived as spam.
I have add two or three keyword to our post related to our website.This is also a good features for my website. Every post contained the two or three related keyword that is a good feature for every websites.
I don't have a single keyword for the whole site. Instead, I use keywords depending on the topic of each blog post.
Of course, all your keywords are likely to relate to your niche. So your niche is the broadest keyword you have. Though I'm sure it's too broad to target, consider competition. I'm sure the long tail keywords are still related though.
Having a wide range of topic is a good thing. But of course, you should always have a main topic in hand. For example, you have a tech blog. To give more variety to your readers, ad in some gaming news and such.