"I am planning to replace the four 811A's in my AL-811H amp. Is there
anything special I need to do to accomplish this?? I have read about "burn
in" but is there anything else?

Remove power. Make sure voltage is zero. Remove plate caps on old tubes.
Remove tubes. Put in new tubes. Replace plate caps. Close cover before
striking. Turn power on. Light up cigar.

Colin K7FM