When I started my blog, it was taking Google up to 2 weeks to spider it. I found that as I made more and more posts, Google became more attentive. Eventually it got to the point that I could find my own posts on Google within 20 minutes of making them.
If you want to rank above millions of other sites for competitive keywords then you have an obvious problem.
What kinds of things to you want to rank for? If it is 'weight loss', 'dating', 'insurance', 'credit cards', that kind of thing - good luck with that!
If it is something unusual like 'forest of bowland ride' - easy! My CycleChat forum ride thread is currently ranked 5 and 6 on Google.co.uk.
If you pick something specialised like 'crud roadracer mk2 review' - easy! I have 2 entries in the top 4. Only BikeRadar outranks me.
I'd say follow thomas's advice.
Remember - regularly updating your blog helps.
Load time is a factor. Don't bloat your site out with lots of huge pictures. Shrink them and link separately to the original large images if you want to.
If it is a WordPress blog, make sure you use a cache plugin to speed your site up immensely - I suggest WP Super Cache or W3 Total Cache. Use a decent hosting company. I used one which was always slow (forgotten its name now!). Hostgator does some good deals but there are many others.
Oh - a very obvious one - post frequently on popular forums/fora that allow you to attach signature links! People click on mine all the time. You'll see that I've made an effort to catch people's attention. I haven't done a lot of experimentation with mine but I'd say word your signatures carefully and play with the formatting. (Don't go OTT though or Admin/mods will step in.)