Hi and welcome to Just Answer!
Have most common IRS publication as your desk references:
Business Expenses - http://www.irs.gov/pub/irs-prior/p535--2010.pdf
Travel, Entertainment, Gift, and Car Expenses - http://www.irs.gov/pub/irs-prior/p463--2010.pdf
Corporations - http://www.irs.gov/pub/irs-prior/p542--2003.pdf
While the IRS doesn't require any specific accounting - you would need to keep records to support your deduction. This publication will help you to start - Starting a Business and Keeping Records - http://www.irs.gov/pub/irs-prior/p583--2007.pdf
While you are not required to use a CPA - it might be helpful - especially if you do not have much experience or do not have time because all your time is devoted to business activities.
Employment taxes are very important part of your business activity. You may use any payroll services to ensure compliance.
You withhold part of Social Security and Medicare taxes from your employees' wages and you pay a matching amount yourself. To figure how much to withhold from each wage payment, use the employee's Form W-4 and the methods described in Publication 15, Employer's Tax Guide and Publication 15-A, Employer's Supplemental Tax Guide .
You report and pay FUTA tax separately from Federal Income tax, and Social Security and Medicare taxes. You pay FUTA tax only from your own funds. Employees do not pay this tax or have it withheld from their pay.
You need to register with the Labor Department in each state you have employees.
In California - it is the Department of Industrial Relations - http://www.dir.ca.gov/
For sales tax purposes - depending on your business activities - you might need to register and apply for exception certificate. That should be done in each state you have a nexus. In California - see additional information here - www.boe.ca.gov/info/reg.htm
Even if your C-corporation is registered in Delaware - you might need to register it in each state you will have business activities. In California - foreign (other state) corporations, have to register to do business in California - see more information here - http://www.corp.ca.gov/
You need to estimate possible tax liability for your C-corporation and might need to pay estimated taxes. Here is the form to use - http://www.irs.gov/pub/irs-pdf/f1120w.pdf
Here are some other federal forms often used by corporations - http://www.irs.gov/businesses/small/article/0,,id=157765,00.html
I hope that helps.
Let me know if you need any clarification.