Plating small parts is easy.  You need a glass container, a square one,
like an old-fashioned accumulator, is perfect.  A plastic one will do
the job as well.  You also do need enough vinegar to fill the container
with.  Next comes a piece of pure chrome.

And the last thing you need is a power supply, 12 volts up to 20 volts
DC.  Go find a cheap switching power supply.  Well, let's start.

1) Thoroughly clean the part!

2) Fill the container with the vinegar.

3) Connect the negative contact of the power source with the part to
be plated.

4) Connect the positive contact with the piece of chrome.

5) Place the part in the vinegar; it should be "swimming" completely
free.

6) Switch on the power.

7) You will see some bubbles showing up, the part will gloom somewhat
blue.

8) The plating will take some hours.  A higher voltage will speed up
the process a little.

9) After the plating the surface will be quite raw and dull.  Use fine
sanding paper.  For high gloss you will have to polish the part very
well!

Instead of pure chrome an old chrome-plated part will do the job also,
if only this part is bigger than the part to be plated.  (Which means,
if the surface of the old part is bigger than the surface of the new
one, there will be enough chrome molecules available to move from the
old part to the new one, covering the new part completely.)

It is common practice, before the chrome-plating, to plate the parts 
with copper first.  This goes exactly the same way as with chrome.
The advantage is that the surface of the part will become smoother,
so there is less polishing to be done on the finished chrome plating.
By the way: a goldsmith or jewelry should be able to supply you with
some pure chrome.

I did read somewhere in a previous MMDigest that what you see is
not the chrome but the underlying nickel plating.  This is not true.
If the chrome plating is done properly (with enough electricity and/or
time) one will not be able to see the underlying metal, neither nickel
nor copper.  Chrome plating on a nickel surface is not a good idea,
since nickel-plating gives a very raw surface, which makes it difficult
to get a perfectly chromed surface in the end.

Jan Kijlstra