Begin by standing on a comfortable surface, where you have plenty of room at each side.
With a 5-lb potato bag 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 relax.
Each day you'll find that you can hold this position for just a bit longer.
After a couple weeks, move up to 10-lb potato bags.
Then try 50-lb potato bags and eventually try to get to where you can lift 100-lb potato bags
in each hand and hold your arms out straight for more than a minute.
I'm at this level.
After you feel confident at that level, put a potato in each bag.