Don't ever underestimate the importance of sanding as it can be the making of a piece.
There is nothing worse than to see a piece that somebody has made and you can see sanding or tooling marks that could have been removed with just a little more time and effort.
Sanding a bowl.
It is important to get as good a finish of the tools as possible as this makes sanding easier and you are able to start with a finer abrasive.
If you have a bit of tear out or tooling marks then start with an abrasive that is course enough to remove them.It is no good starting with say 320 grit to remove tooling marks or tear out it simply will not work.Start with 80 grit if that is what it takes to remove any marks and and tear out.
When you are sanding your bowl slow down the lathe to about 500 rpm and sand across the bowl using very light strokes.This applies to the inside, rim ,and underside of bowl.
Do not press hard with your abrasive as this will create heat and wear out the abrasive.When you have finished with your first chosen grade of abrasive you should have a good shape that is free of tear out and tool marks .If it isn't take the time to go back and do some more sanding as this is the most important bit.
If you are now satisfied with the finish you have achieved with the chosen grade of abrasive move on to the next grade.The important thing to understand is that each grade of grit can only be expected to remove the sanding marks that the last grit left.Never go more than 100 grit apart in other words don't expect 320 grit to remove marks left by 80 grit it wont.
It is also a good idea to wipe the bowl over with tack cloth between different grades of abrasive as it is possible that some loose particles of abrasive can be left on the surface.
If you find after sanding to say 320 grit and you can still see marks don't keep using 320 grit go back to say 120 grit or 240 grit and work your way up again.Do this as many times as is necessary as it is the only way to get a perfect finish.
Another thing to remember is that worn 240 grit abrasive is not 320 grit abrasive.When it has lost its sharpness it should be thrown away and new abrasive used.
Hand sanding is something I very rarely do anymore as it is slow and hard to achieve a surface without slight sanding marks.
Most of my sanding is now done with the Simon Hope Pro sanding system.I have found this system to be so much quicker and more efficient than hand sanding.For some time I used electric drills for power sanding but found the bearings on the drills wore very quickly and the noise of an electric drill can soon get on your nerves.
The beauty of the Simon Hope system is the the head revolves at the speed the revolving wood wants to be sanded at.
I have no connections with Simon Hope and I get no rewards for recommending this tool the only reason I recommend it is because it really does work.
There is another similar system on the market but it is nowhere near as good as the Simon Hope system as The Simon Hope system has free running bearings and the other system has not.
Sanding Between centres.
All of above applies when sanding between centres.
When you sand between centres the grain is running parallel with the lathe bed therefore as you sand with the piece turning most of the time you are sanding against the grain.It is very important to keep the abrasive moving briskly from side to side.Obviously this is not possible when you are sanding coves or beads but the sides of coves and beads are actually side grain therefore they are OK to be sanded without moving the abrasive from side to side.
Good tooling is more important on spindle turning so as to retain the crispness on coves and beads Etc.
It is very easy to sand away detail when sanding between centres therefore more care needs to be taken.
Another good tip is to stop the lathe between grits and gently hand sand with the grain.