Assuming that for your FIRST half marathon your goal is to simply finish in good style (ie not in an ambulance or vomiting on your self) here is what I recommend for a half.

Fitness training:

First gradually build a cardio base up to 45 min 4 days a week -THR zone 2-3. Take your choice from hill walking to recline bike to road bike to elliptical trainer and MIX IT UP. Include core strengthening as well. Rest every other day. Once you've got a good cardio fitness base (should take several weeks to 2-3 months to get to at least depending on what youre starting from) you can move on to training for an event.

Performance Training:

For a half M, you really don't NEED to run more than twice a week if you do cross training and strengthening as well.

For my fist half M, I trained with the following -

Monday - HIIT intervals on bike and inclined eliptical emphasizing speed over intensity. About an hour of hard n fast work in zones 1-5.

Wednsday - Tempo run of 45 min. This could be on a tread mill or track but make the intensity moderate (zone 3, not easy or hard). Then do 30 - 45 min of biking again in zone 3.

Friday - Hill climbing, steeper is better. This is for strength building and it could/should be a combination of hill biking, stair climbing and steep incline eliptical intervals. You can throw in some hill running if you want as well. About an hour total time of heavy work in zones 1-5.

Sunday - Long easy day. Jog/run from 2-3 hours gradually building (adding 1-2 miles per week) up to a 10 or 11 mile long day exactly one week prior to your race. This is zone 2 stuff and is meant to accustom your body to distance movement, build mental endurance, and build fat-for-fuel abilities.

Taper down in the final (race) week but do a 1 hour session on Monday and a 1 hour session on Wednesday and skip Fridays session altogether - race on Sunday.

Don't forget the importance of stretching, nutrition and circuit/core training as well - to be done right after your cardio workouts on the same day. Full recovery days between sessions.

You should be running at least four times a week, with one long run a week of 8 to 10 miles before your first half marathon. Build up your base mileage one or two miles a week at a time, to 20-30 or more miles per week, divided between four or more sessions.

For your first marathon, you should again run at least four times a week, and with one long run once a week. Build your weekly mileage up one or two miles a week until you have 30-40 miles a week or more.

I just read an article about the FIRST program from the Furman Institute of Running. They are gathering research on a 3 day running training program which recommends 2 days of cross training in addition to the 3 intense running days. I think I'll try it.