About primary vs. secondary partitions.

[Jose Albores]

I read somewhere in the list, that there is a limit of 4 primary
partitions on one drive.
Just to know:
What of Linux should/must be on a primary partition and what on a
secondary?
Let's suppose I want to have two swap and three linux native partitions:
All swap should go on a primary? Or one and one?
And about Linux natives: should them all go on a primary partition? Or
just "/"?
TIA.

-- 
J. M. Albores