how to book
 

I'd like to see how I do booking our flights rather than letting the TA or travel company do it, which is what we usually do. Here's my problem-for our cruise we fly from Dallas into Barcelona, and at cruise end we fly out of Venice to Dallas. Is something like this booked as 2 separate one way flights, or is there a way to make it all one ticket even though we enter and leave Europe at different airports? Many thanks!

It's called an open-jaw ticket (you fly into one city and return home from another). People book trip like this all the time and it is very easy to book as a "one ticket itinerary" on any airline website. Simply, use the "Book Flight" link and choose the "Multi-city" option. For flight segment 1 enter your US "FROM" airport (in your case DFW), your "TO" Airport (in your case BCN), your planned departure date, Then for Segment 2 enter the airport code for Venice (VCE) in the "FROM" box, your planned departure date and your home airport (DFW) in the "TO" box. Click "submit" and Voila! - you'll get a list of the available flight.

RoamsAround-Many thanks! You do make it sound easy. Am I correct that this isn't the kind of flight for which I can use sites like kayak, cheapoair, etc.?

No, you are not correct. Use the Multi-city option.

You can use the companies you name and many more. Specific airlines also sell open-jaws tickets which cover their partner airlines. So Delta, for instance, can set up routes served by KLM, Air France and sometimes Alitalia for the trip you have in mind. Buying directly from the airline may be a little cheaper.
You will probably stop to change airplanes on these flights. The fewer stops, the better. Pay attention to the time allowed for the connection. Anything under two hours deserves caution, in my opinion, even though airlines sell shorter connections that leave little room for delays.

You guys have been very helpful. Southam-You are so right about connecting times. Anything under 2 hrs. makes me a little nervous.