Ivan,
I don't think tape on the crank-spindle interface is a good idea. Since the Teflon is a solid material, there is a chance that is could bunch up, or get trapped as the crank is installed. Even if this doesn't happen you have put something between two surfaces that are designed as a precise press-fit.
Personally, I am in the habit of smearing a little grease on the square taper before installing cranks - but arguments have raged about whether or not this is correct. I believe the manufacturers recommendation is to install square taper cranks without greasing. In my case, the bikes see the road all year, in all conditions and I prefer all metal interfaces to have some protection against corrosion and seizure. I've never seen any ill effects from this approach with cranks - never come loose, never have a problem removing them. Octalink cranks come with instructions to grease before assembly.
Cheers,
Ed
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