How to Create or Move Site Collections into Separate Databases of SharePoint

I had a requirenment to split\move a bunch of site colletcions using same
content databse into their own respective content databases.

Here are the
steps i followed :

1. Create a New Content Database -
Goto Central Admin site -> Application managment
-> Content databases.
Choose your destination web application from the left top corner.( the one which
will carry all the content databases) and Click on "Add a Content database". See
the screen below.

2. Now give this database an appropriate name (according to your site
colletcion) and hit Ok. The Database server should already be listed, if not
then please enter the database server name too.

3. Now, on the "Manage
Content Databases" screen click on the previously used content database. I mean
the one with "Site Level Warning" and "Maximum Number of Sites" set to 9000 and
15000. (In most cases).

4. Adjust Site Level Warning and Maximum
Number of Sites - Once you open the previously used content database,
Set the "Site Level Warning" to the current number of sites in the content
database and the "Maximum Number of Sites" to one Plus the current sites in this
content database. For e.g. in the screen below I had "2" "Current number of
Sites" in my old database so I will adjust

Site Level Warning - 2 and
Maximum Number of Sites - 3.

5. Now you all all set with your database configuration. Now you can simply
backup your site collection from the source web application (could be same as
destination web application) and restore it in this webapplication (the one
which has the new content database). I used stsadm command for this.

The New site collection will get created in the new content database.