Begin by standing on a comfortable surface, where you have plenty of
room at each side.

With a 5-lb potato sack in each hand, extend your arms straight out from
your sides and hold them there as long as you can.

Try to reach a full minute, and then relax.
Each day you'll find that you can hold this position for just a bit
longer.

After a couple of weeks, move up to 10-lb potato sacks.
Then try 50-lb potato sacks and then eventually try to get to where you
can lift a 100-lb potato sack in each hand and hold your arms straight
for more than a full minute. (I'm at this level.)

After you feel confident at that level, put a potato in each of the
sacks.........