I'd suggest reading Bernstein's 'The Intelligent Asset Allocator' -- this will teach you the basics of asset allocation (and the math/stats/data behind it).
I think that DCA can be helpful psychologically -- ie, you have 24K to invest, so do it by putting in 2K every month for a year. This way, you ease into investing (which terrifies a lot of people), and you practice a bit of buying low & selling high, as in, you buy more of a stock when it is cheaper, and less when it is more expensive because you are putting the same fixed amount in.
DVA (dollar value averaging) is similar but slightly more complex -- you essentially (taking the prior example of having 24K to invest, nothing invested currently) decide that you want to have a certain amount after every month, ie, 2K more than the prior month. So, if you put in 2K in the first month, and it went up to 2.5K by the next month, you would put in just 1.5K to bring you up to 4K. On the other hand, if your assets went down in value, to 1.5K, you're contribute 2.5K to get to the 4K. You're essentially also trying to buy more when assets are cheaper, and buy less when they are expensive and doing well.
That said, I've personally always just put in a lump sum -- I save for my Roth IRA contribution during the prior year, and then come January 1, put in the $5,500 (current max for people my age) in. My thought is that since the market generally trends upwards, it'll benefit me to put in the money earlier instead of later. I'd also note that while I firmly believe predicting trends in the short-term is quite silly, there has been a slight positive correlation found for asset price month-to-month. It's not large -- about 4% of an increase/decrease in price can be tied to the prior month's increase/decrease in price. But it does mean that re-balancing very often isn't necessary, and perhaps a bit harmful relative to re-balancing once a year. (And when I contribute each year, I basically contribute in a way that puts me back to my target allocation) Bernstein mentions it in the book I recommended above, using the example of US/Japan equities -- for a decent period of time, increase in value of US stocks corresponded to decrease in Japanese stocks -- if you had rebalanced frequently, you would be much worse off than if you had rebalanced less frequently (ie, once per year).
I was actually just discussing the 'ideal' frequency for re-balancing with my boyfriend -- I tried to convince him that once a year is ideal for your average buy-and-hold investor: it's long enough to take advantage of slight momentum, but short enough that if your asset allocation goes way off your intended allocation, you can re-balance and make sure you've got an appropriate level of risk (as opposed to way higher than intended because stocks did well and grew to a significant chunk of your portfolio).
