Copying data from table to table (cloned tables)

Hello all,
Any one could suggest the best way to copy data from table to table in the
same db, the reason why am seeking for this is that the first table is
becoming very big, and old data has no reason why to stay there, so i
created a cloned table but without indexes and constraints (lighter) and now
i would like to copy 'some' data from first to second table (copied data is
data older than 3 months, i have a timestamp column).

In other way, i have a table called 'hotqueues' where i store fresh messages
queued, once messages are treated, they stay in 'hotqueues' but with a flag
indicating that their arent queued for treatment..
so in this way, data will rest there forever, slowing down any searches in
that table, the solution was to copy old messages to another table called
'coldqueues' that has the same structure as 'hotqueues' but lighter (without
constraints and indexes).
How to copy these data with 100% data-loose free.

Thanks for any help you can provide.