When it comes to travel expenses, it all depends on the reason for travel and the amount of work done.
If the trip is entirely for business and in the US, you can deduct all expenses. If it is primarily for business, then only deduct the business-related expenses and the to and from the destination, but if it is primarily personal you only deduct business-related expenses and not the destination.
However, if traveling outside the US, things are pretty similar except if the trip is primarily for business. If at least 25% of the trip is spent on non-business activities, then only deduct business-related expenses to and from the destination between business and non-business activities.
Meals and entertainment are more complicated, but nonetheless, only 50% can be deducted and when it comes to spouse or gifts only if they serve business purposes.