How to choose levels.

Small Torpedo LevelMany DIY jobs depend upon key aspects of the project or reference points being perfectly horizontal and level and this is why spirit levels are so important. Some levels also incorporate a 45 degree angle also.
Ideally a DIY kit should contain, in order of amount of use, an 8 - 12 inch torpedo level which is ideal for pictures and small shelves, an 18 - 24 inch level as the projects or level line become longer upto a 4 foot level for bigger projects.
The amount you spend on a level does determine the accuracy of the the level, how long the level remains accurate and the amount of "heavy handed" use it will take.
The build quality of the housing of the veil in which the bubble can be found is critical to the quality of the level and accuracy. In a cheap level it is likely that the housing will be week and a few gentle taps or drops on the floor will knock the level out of true.
In order to extend the life of a level never knock it or drop it. Avoid leaning them against walls where they will slide down. Some levels have rubber ends to reduce the effect of knocks and drops.
2 foot levelAlways check if a level is accurate before using it. To do this find a relatively level surface and place the level on that surface and note the reading. Now flip the level round on the same surface. If the level is accurate the second reading will be identical to the first reading. If the readings are not the same then the level is "out" and should be marked as so and replaced.