Another option (slightly more complicated than DCA) would be value cost averaging. Like DCA, you pick a target amount to add each month. You also pick a target growth rate - the rate you think the investment should return, on average. Each time you invest, you compare how your 'stash has grown to the target growth rate, and adjust your additional investment amount by the difference.

As an example, say your target is $10000/mo., with a target growth rate of 6% annually (picked for easy math). The first month you put in $10000. After 1 month, at 6% annual growth you'd expect about a .5% increase on average. .5% of 10000 is $50. If you have $10050 in the account after 1 month, then you're right on track and you invest another $10000. If the market did really well and you have $11000, then you reduce your additional investment by the $950 difference and only put in $9050. Likewise if the market crashed down to $7000, you put in an extra $3050 in addition to your $10000.

For the 3rd month, you'd expect $20050 + .5%, or $20150.25, so if it's more or less than that you again adjust your contribution.

This method requires more work than DCA - you have to check it every month and do a calculation - but enhances the "buy more when stocks are cheap, less when they're expensive" effect. You also have to have a good estimate of the return (at least for the average return over your investment period) - if you guess too low, then you won't be putting money into a winning investment as quickly, and if you guess too high then you'll be throwing more money than you wanted at it for less return than expected.