Most people who come to Dallas are going to come by air since Dallas is home to DFW, the Dallas Fort Worth airport, one of the largest airports in the country by passenger volume. Details for each method of arrival will follow:

By plane
There are two major airports in the Dallas / Fort Worth area, DFW, and Love Field (DAL). Love Field is smack in the middle of the city (to the north) but has certain restrictions on flights into and out of due to the Wright Amendment. Love Field is home to Southwest airlines, so if you are flying from within Texas, check out the flights on Southwest. COM Otherwise, you will probably end up flying into DFW. DFW is a large airport, reasonably clean, and during tourist-travel type times (not AM/PM Monday/Friday "flight rush hour") lines are short and staff is friendly. Equally positioned between Dallas and Fort Worth, DFW is a great airport to fly into.

No matter which airport you are flying into our out of, if it is during rush hour, traffic will be a factor! Make sure you budget at least 2-3 hours to get to/from the airport if you are traveling on I-635, the Bush turnpike (SH-190), or 75 (Central Expressway). It will probably only take you an hour (and traffic has been getting better lately), but it is far better to have that extra hour of cushion than to be stuck on *the one road* that will get you where you need to go, and to be moving at a crawl. Once you've arrived at the airport, you will probably do best to take one of the Shared Ride shuttle services. They offer door to door pickup and drop off, probably costing ~$30 for ~20 miles (which will get you to most places). For DFW, there are courtesy phones that will let you ring them directly (for free), and they are usually pretty quick about pickups and drop offs. (at most adding an extra 30-40 minutes while you wait for them to pick up more people, or to drop your fellow passengers off on the way to your place or hotel).

By train
 • Amtrak - Two routes serve Dallas/Fort Worth: 'Texas Eagle' (San Antonio to Chicago) & 'Heartland Flyer' (Fort Worth to Oklahoma City)

By car
To get here from Oklahoma, take I-35 or US 75 south. To get here from Houston, it's ~250 miles north on I-45 (which turns into 75). To get here from Austin, take I-35 North. To get here from Louisiana, take I-20 east. Dallas is pretty much the junction-point for most cities within a 2-300 mile radius, with good road service to and from. Any map of the United States should have enough information to get you into Dallas with no problems. However, once you are here, watch out for traffic. Traffic tends to go towards the city centers in the morning, and away from the city centers in the evening. Major choke points are 75 South in the morning (what takes 20 minutes with no traffic, ends up taking 1-2 hours with traffic). I-635 near 75 is also usually a mess since I-635 (being the beltway that runs all around Dallas) is an often-traveled road. Also watch out for I-35E southbound in the mornings.

75 is also called "Central" or "Central Expressway", and turns into 45 just south of Downtown (note: 75 is an expressway, because 75 has too many entrances and exits to be considered a highway). I-635 is sometimes called LBJ, which stands for Lyndon B Johnson. Note, there are two branches of I-35. I-35 splits into I-35W at Denton (30 miles north of Dallas) through Fort Worth to Hillsboro (50 miles south of Dallas), and I-35E that runs from Denton through Dallas to Hillsboro. After I-35W and I-35E reach Hillsboro, they simply rejoin as I-35.

By bus
Bus service shouldn't be too difficult to encounter. There is a Greyhound terminal near the center of downtown. Buses also run to and from Shreveport on the weekends, which is sponsored by the casinos. This is more for the locals to go and get their gambling fixes, but ask around if you're interested.