Smoothing out the google dance

Hi
I have an aged website which does OK for a number of keywords (top 10). I have been trying over the last three months to rank a different k/w of medium difficulty. Taking a longer term approach I have been building slow but steady links (15-30) a day, with a variety of types used.
The difficulty I have is that (using serpbook) my rank can vary by:
day 1 - 50
Day 2 - not in top 300
Day 3- 50, later in day 3, not in top 300
day 4- nt300
Day5 - 32
Day 6 - not in top 300
and so it goes on and on.

How can I stabilise this?

It depends on Google, its a lot of things that cause this.

But after you stop building links and google calculates them all you will get a more accurate ranking.

If you keep building links google will keep doing calculations and the dance will continue.

Also try using another serp checker, I found serpbook to be really bad the last 2 months.

I was tracking 10 keywords on serpbook and they did not show any rankings for 1 whole month I was about to go crazy.

I put them keywords into http://serplab.co.uk and they were ranking in the top 10.

serpbook works fine for my older sites but anything new I add just doesn't get picked up accurately.

What kind of links, you use? I suggest to you, get more web 2.0 and Social Signals - This kind of links give you more stability. The second thing is that member:asap1 is right: Try using serplab.
Peace!

Thanks to both. using a variety of links, blog posts, small pbn which I own, web 2 etc. Think it is just the extreme volatility that surprises me. Going to use serplab as suggested. Thanks.

Serlab is not very precise too.