Look for heavier, thicker grades for longest life. Large hoods are a nice feature if you plan to cook sizable items or add a rotisserie. Top-rated burners, cooking grids and grates are made of stainless or porcelainized stainless steel, cast or brass. More affordable models will feature lesser grades of steel or galvanized steel. Some burners are individually controlled, with a dedicated igniter beneath each cooking area, so you can adjust for high heat output on one end of the grill and slowly cook foods on the other.
Some models feature as many as six burners.
Side burners are usually highly rated when it comes to BTU output, and are made of stainless steel as well. Burners are rated by their BTU output, which is a good gauge of firepower. Another specification for comparison you will find in most manufacturers' brochures is available square inches of cooking space, often split between a primary and secondary cooking surface. This gives you some idea of how much food you can cook at once, but be sure to review the breakdown of the total cooking surface to make sure it includes surfaces you're likely to use consistently. The same is true of wok rings, rotisseries and griddles.