1. Buy a stock that you expect to decrease in value in the short term, but to make money in the long term. You pay, say, $10,000.
2. It drops to $5,000. Sell, you can mark off the $5,000 loss on your taxes.
3. Wait 30 days, then take that $5,000 and buy the same stock again. You can still take the $5,000 loss, but if (when) the stock finally appreciates, you make money there, too.
What about following plan.
1. Put $10000 in bank.
2. Wait 30 days, buy $7500 of stock and $2500 for taxes.