But there are various options check out in cisco.com
Either
you can register in java.sun.com or in your near by prometric center
Which exam should I take 640-801 CCNA or 641-821 INTRO Beta
?
it depends on your interest check how to prepare for more details. But
some people prefer to write certification with more objectives so that
they will learn a lot.
Will
the score be displayed on CCNA certificate?
No. it will just say "you have successfully passed" nothing
else regarding your score
How many attempts can I
make to complete the test?
As many as you want ,there is no limitation on the number of tests. But
you should take some time before attending it again. check the
cisco.com site for more information