Recently my bike rear wheel was hit by a car at a traffic light. Now it's bent a little and touches the brake. It cannot be fixed by adjusting the spokes and I am going to need a new one. My bike is Schwinn varsity 1200. Here are pics of the wheel.
Look carefully at the tire, there should be markings on it that indicate what size wheel it is - generally 700 is a road-bike standard. 26 inch is a mountain-bike standard.
This is a good resource.
Also an option is the number of spokes, the more there are, the stronger and more abuse resistant the wheel is generally. Also consider do you have Shimano or another drivetrain- there can be compatibility issues.
You need to match:
- The basic wheel size -- diameter and (less precisely) width. (Tire markings give you this info.)
- Brake type -- rim or disk. (Yours is obviously rim.)
- Axle style -- solid, quick-release, thru axle. (Yours obviously QR.) There are also variations in axle diameter, for solid axles.
- Freewheel or freehub. (I think you have a freewheel, but not 100% sure.)
- Number of cogs. (Looks like you have 7.)
- Overall hub width, measured as the distance between dropouts. (Usually there is only one possibility, given cog count, but there are a few odd cases).
As to number and weight of spokes, that's up to you, as is the degree of "aero" shape of the rim. These factors don't affect interchangeability.