There recently was another post about this, was very informative but I can't seem to find it at the moment.
The main things to look out for are:
Gallons Per Day (GPD)- I got one thats 60 GPD more than enough for me, I got a rubbermaid container and a float valve kit.
Make sure to get one that uses a TFC membrane, anything over 75 GPD (I think) uses dual TFC membranes, which you'll need a special shutoff kit for the float valve to work.
Get one with a pressure gauge and a TDS
meter, you will need the TDS
meter to so you know when you need to change the DI
Get a DI
unit with color changeing resin and uses the standard size resin cartridge. http://www.marinedepot.com/md_viewIt...product=RO1153
To save money at first or If your gonna use it for drinking water too just get a RO
unit, you can easly add on a seperate DI
. That way you can splice into the line easier to get your drinking water before it goes on to the DI