If you or your employees attend conferences or meetings associated with your business, the costs associated with these meetings are at least partially deductible. If you fly to your destination, you can usually deduct the cost of your plane ticket. You can deduct the cost of driving to the meeting using the IRS standard mileage rate. The IRS generally prefers you travel the cheapest way.
Regarding meals and entertainment, this document will give you all the details you need regarding deductibility. If you have other miscellaneous expenses, such as tips, you can generally deduct them in full as long as they are reasonable and you keep your receipt.