If you are registered at the State and Federal level (IRS) as a Subchapter (s) (Disregarded entity in IRS parlance) your LLC will not pay taxes except for state sales taxed on what you buy. The expenses and the revenue flow through to the owner's personal tax return.
In terms of preparing for tax season, insure your LLC accounting system (either manual or automated) clearly identifies only business expenses. Most small firms utilize a business credit card for this purpose and never use it for personal purposes.
I suggest you use the Small Business and Self-Employed Tax Center at the below link to determine what you can deduct as wall as the nuances of self-employment and your business:
https://www.irs.gov/businesses/small-businesses-self-employed