I'm sure that this subject has been explained before but new Forum Members may not be aware of the technique. Here is a photograph of a Premium Bitter that was bottled back at the beginning of the year and stored in a flip-top bottle. It has very little head because I poured the beer out slowly to save disturbing the yeast at the bottom of the bottle; but the CO2 is still in there so ... ... this is the same pint about ten seconds later ... ... after I pulled about 2ml of the brew into a small syringe and "blasted" it back into the glass below the surface. The lack of a head doesn't affect the taste but it does make it look a bit nicer; so I do the syringe trick only when I am serving a brew to a visitor. Enjoy!