Yes, on should do their homework but... Don't forget this is FAQ section. It is, at least, better to ask here than opening an account at dodgy SB firm and lost all of it. Newbies may even ask the most elementary question such as what is bid/offer S/R etc. It is nothing wrong with that. All traders share one common thing- to win and make money. I like someone's signature that says something like.. don't look down on anybody unless you are trying to help him up.
Ok, for my 2cents, I can say one can trade Dow in various instruments
1. dow futures- big DJI or mini-dow CBOT futures (out of hours tradable, small spreads)
2. DIA - an ETF (as a stock) mirroring DJI (only market hours)
3. CFD - US30 (spreads wider after hours)
4. spreadbet (largest spread, after hours tradable)
My recommendation is no.1 if you can spare $7000 and above to trade 1 ym contract. As for broker I recommend Interactive Brokers (IB).
For no.2, you'll need $25000 if you wan to day trade. IB is still good for that.
For no.3, I used CMC before but only good for low contracts up to 10 may be.
For no.4, there are many good SB firms. I like Finspreads and Etrade. Search SB section for details.