Are you deploying these web  parts via solution files? This method ensures that
all features, web parts, etc. are deployed equally across the farm.

However, we are deploying using CAB files. We
tried to install using solution files but always ran into something probably
because we are missin g something.

Is there any good resource that you can refer to to install using solution
files?

Just a small recommendation: avoid WSS Extensions for VS, as this obscures
some of the deployment  process and will not serve you well as you change
environments.

We use CAB files to deploy. We tried
using solution files but could not succeed.

Can you point to some best practices  or some guidelines on using
solution files for installation?

high level overview will be in the sharepoint  Best Practices book:
www.amazon.com/.../0735625387

Free stuff is at:
msdn.microsoft.com/en-us/sharepoint/default.aspx (be careful with the
extensions, but rumor has it the next version will be much better)

and

www.microsoft.com/click/SharePointDeveloper/