My wife will be coming to US in B1/B2 visa. I am in a H1B visa. Please let me know whether I can get tax exemptions if I file tax returns with my wife in B1/B2 visa or should I process dependent H4 visa for her inorder to get any tax exemptions.
Also please let me know the process to file tax returns with my wife being in B1/B2 visa. Any help is highly appreciated.

You can file joint return as residents. You must both report your worldwide income.
If you have any foreign income, and on that income you paid taxes in the foreign country, then you can claim foreign tax credit (Form 1116) or you can use Foreign Earned Income Exclusion (Form 2555). Your U.S. Tax Return: U.S. Citizen or Resident with Foreign Income (http://taxipay.blogspot.com/2008/03/us-citizen-or-resident-with-foreign.html)