If you are going to buy your Dream Bike then you must consider the following Aspects.
1) Budget: Firstly Check Your Budget Because Bikes, Car are nothing but liability not assets so if you are low on budget then just hold to buy your Dream bike or Change your Dream Bike;P
The things comes under the Budgets are:(i)Bike Price(ii)Mileage(iii)Maintenance
2) Suitable: If your Dream bike is on budget then the second thing to consider is to check is your Dream bike is Suitable to Your Personality. eg. suppose a Rich Guy with tiny body has dream bike of Hyabusa then he should consider another options in Bike Because Hayabusa is not suitable for tiny guys.
The things you needs to check with respect to your personality are:(i)Bike height(ii)Bike Weight(iii)Bike Length
3) Test Drive: If your Dream bike is on Budget & also Suitable to your Personality then the biggest thing you must do is go for Test Drive. Test Drive is Must For buying any Bike, not just for your Dream Bike.
Aspects You Must Check with the Test Ride are:(i)Riding Comfort(ii)Road Grip(iii) Engine Response or Throttle Response.(iv)Breaking of Bike.