I worked in Garland for quite a few years until fairly recently. Overall, Garland has some gems, but it is generally an older inner-ring suburb with aging neighborhoods, and overall doesn't have the drawing power of some other older suburbs such as Richardson or Plano. Like many of the older DFW suburbs, you'll find that as the housing stock gets newer, the homes tend to trend larger as residents moved up from starter homes in the 70's-80's to larger homes in the 90's-2000's. Ironically, as a result in some cases, you'll find that some of the older neighborhoods have turned over with new families moving in, while many of the neighborhoods developed in the 90's are largely empty nesters at this point. This also affects the school populations, so just something to keep in mind.
Generally speaking, the largest shopping and dining hub in Garland proper surrounds Firewheel, off of the Bush Turnpike in north Garland. Residents in the southern end of Garland largely go to either north Dallas, Mesquite (also an aging area), or Rockwall to shop. The traffic around the 635 corridor to the south is generally terrible, particularly with the multi-year 635 expansion project currently taking place.
Do be careful with neighborhoods from the 70's and 80's if they were originally developed by Fox and Jacobs (your realtor should be familiar with them). They were a major developer across DFW during that era and many of their homes have since become known for generally poor construction, particularly foundation problems (common across DFW as a whole, but even more pronounced with Fox and Jacobs).
Housing-wise, if you are working on the north or west sides of Garland, I would also look at Richardson, Plano, Murphy, Sachse, and Wylie. Do keep an eye on the school district boundaries, as these do vary from the city limits and can affect housing/property prices quite a bit. If you are looking west of Garland, avoid the area roughly where Skillman and Forest cross 635, these are some of the roughest neighborhoods in Dallas (mainly due to seedy apartments). The area to the southwest of there is Lake Highlands, which is in Dallas city limits but Richardson ISD, and is generally very well regarded but with expensive housing. As a general rule of thumb, avoid Mesquite to the south of Garland.
Downtown Garland has seen quite a resurgence in recent years, and is definitely worth a visit. Intrinsic Smokehouse has great BBQ and live music.