What style of mixer is best?
The style you need depends on what you'll be primarily mixing. Items of a more liquid consistency are best controlled by an immersion blender, where you can have the most control over where the mixer goes and how fast or with what frequency it mixes. Pizzerias or large-volume bakeries will tend to be best served by a floor model style, where higher horse power and larger capacities will help keep large batches of dough under control. For smaller tasks, such as one or two batches of cupcakes or cookies, or occasional light to medium-duty mixing, a countertop style will work just fine.
How much horsepower is right for my mixer?
The amount of horsepower needed is defined by how much you mix, its consistency and how often you mix it. For a large bakery or pizza place, where bulk amounts of dough are made at one time, a 2 to 3 horsepower motor is the best option, because it will stall less when the dough reaches its thickest consistency. For other applications in large batches, such as hummus, coleslaw, thin batters, or other items that don't reach a very solid consistency over time, a 1 to 2 horsepower motor would be fine. Lastly, for simple medium to small batches of sauces, batters, and other dishes, any horsepower at or below 1 will work. Be careful when choosing your mixer, horsepower is key. Too powerful a mixer and you'll end up with a large mess, and yet too weak a mixer will leave jammed gears and frustrating repairs, so make sure you take into account what you're mixing when choosing horsepower.
Which attachments do I need?
Attachments are usually rather easy to choose. For large amounts of dough, dough hooks work best, as they control the dough and mix it properly in the least amount of time. For lighter loads, such as whipped topping for desserts, or sensitive egg-based items such as souffle, a beater attachment is best, because it can operate at the slowest setting to gently fold in ingredients. Cake and cookie batters and scrambled egg dishes with mostly liquid consistency and a need for thorough mixing will be best controlled by a whip attachment.