Now you have just brought that shiny new airbrush home.  What do you do first?  I would suggest that before you load it up with paint, you first try out the action.  In the case of a double action airbrush, make sure that the trigger moves smoothly fore and aft as well as up and down.  At this point if the trigger is sticky or you feel a roughness (as in unpolished surfaces), you might be thinking about sending the airbrush back.  This decision is sort of based on the cost of the airbrush.  Obviously, if you are talking about a $30 special, well you can’t expect too much, however, when it is $200, you have a different set of expectations.  Examine the needle and the tip for damage or defects.  Pull back the trigger.  Is the needle centered in the tip.  If not, loosen the needle and give it a rotation.  If the needle’s position changes with the rotation, then the needle is off.  If rotation does not change the position, then there is more than likely an issue with the material tip.

After doing your preflight, load the airbrush with some water.  Check to see that you are getting an even consistent spray.  If you see sputtering, check to make sure the head is tight against the body of the airbrush.  If you have an air cap, make sure it is tight.  If the sputtering persists, then you need to think about returning it.  Chances are you might solve the problem with some wax between the head and body of the airbrush, but the manufacturer should be able to do better than that.  While spraying, hold the airbrush up to the light.  You should see a pattern that is parallel with the airbrush, Figs. 15-16, not angled as in Figs. 17-18.  If after all this, you are satisfied with the performance, keep it.  If not, send it back and you won’t have to worry about explaining the paint residue.  I strongly suggest doing a thorough check of your new airbrush.  I’ve had to send back very expensive airbrushes, so spending a lot of money is no insurance against manufacturing defects.

Airbrush Operating Tips
Paasche H
The Paasche model H has long been regared as a "work-horse" by many modelers. However, this video presents the design and function limitations of the Paasche Model H, in regards to producing the smoothest possible surface finish for scale models, and why it may not be the best choice.
"Choosing the Right Airbrush" by Coast Airbrush

Three very informative videos, produced by Coast Airbrush, presenting all the features to look for when making an informed decision on what airbrush to purchase. Coast Airbrush is the premier airbrush retailer in the Unitied States and my first stop for anything airbrush.