For keeping track of our expenses we just save all of our receipts and keep them catagorized (Animals, Supplies, Food, Vet and Business ie. Traveling, Lodging, Meals, Gas, Mileage and Maintance on the car). Then when we go to our Accountant to file our taxes we just go thru and Total up each catagory and that is what we give to the accountant. They really don't want or need you to bring in the receipts for everything. Keeping the receipts is for your personal records if you were to ever be audited.
As far as what you need for taxes. Save everything! Bring in the totals for all of your directly related expenses that I listed before. And copies of all of your household bills. Cell Phone bill, electric bill, gas bill, internet, mortgage/rent, car payment.