If you haven't used U2U CAML Query Editor yet, you can get it here:

U2U Caml Query Editor

It's a very easy to use application. First thing you need to is to Click "Connect".

caml1.png

Then you will have to write your Sharepoint Portal URL:

caml2.png

Then Click Connect. And you're free to use this tool. Click on a List Object and then Choose "New Query".

caml3.png

What we're going to do is to get all the items in a List.

The most easiest way is to get all the items whose ID are greater than and equal to 0.

caml4.png

Write these values and then click Execute query which looks like this:

caml5.png

Here is the result:

caml6.png

See? We got all the records.

Here I'm also giving the CAML Query:

 <Query>
   <Where>
     <Geq>
       <FieldRef Name="ID" />
       <Value Type="Counter">0</Value>
     </Geq>
   </Where>
</Query>

Hope it helps.