On what to do physically, my recommendation is to use mediation beads (aka mala beads). 6-count breathing (6 on each inhale and exhale) and move one bead each breath. With the standard 108-beads, you start at the mala and it takes about 20 minutes to reach the end (you feel your fingers reach the mala again).
I don't go in for doing the same thing over and over like some Buddhists like to do.
It's just a timer, which I set for 3 to 5 minutes. When the timer reaches 0, (part of) a particular song plays. (And a record is made of the start and end times of the meditation session.)
In the rare case that I am doing something other than meditating when that song plays, I know I got so distracted that I did not even notice I got distracted -- which I take as a sign that I have an unusually pressing need for meditation that day.
Do you find that 3-5 minutes is enough? I just tried meditating for the first time, and set a 5 minute timer. When it went off, it felt like only 2 minutes had passed and I could have (and wanted to) go on longer.
The effect I am going for is to reduce my body's production of stress hormones. Consulting a clinical psychologist and Googling around on the phrase "mindfulness-based stress reduction" lead me to believe that 4 minutes a day suffices to get that effect.
Also, those 3-5 minutes sometimes cause subjective experiences of increased calmness that tend to last the rest of the day.
It probably takes longer durations to achieve some of the other effects commonly ascribed to meditation (e.g., becoming more contented). I have tried longer durations, but I judge that in my particular case they are more likely to be harmful than helpful.
Specifically, I have a bit of a chronic health problem which necessitates that my immune system remain always strong and active. Getting too much sun and not getting enough sleep are 2 things that personal experiences lead me to believe are bad for me -- and according to immunology researchers, those 2 things suppress the immune system. The suppression tends to last only a few hours or a day, but that is long enough for me to notice bad effects. Meditating for hours at a time produced subjective effects in me similar to the effects of those 2 other things that suppress my immune system.
So, that is one reason I avoid long meditation sessions and tend to advise other people with chronic health issues similar to mine to do the same.
Sometimes (particularly, in the rare situation described in grandparent in which the first meditation session of the day ends with me looking at a web browser, looking at some file on my computer or doing something else other than meditating) I do 2 to 4 sessions (of 3 to 5 minutes each) a day, and I have not experienced the adverse health effect mentioned above on such days.
By the way, a large part of time I am meditating I am resisting urges (the theme of the OP) rather than doing what most meditators describe, namely, resisting attachment to or involvement in sensations or resisting dwelling on regrets about the past or worries about the future. Specifically, urges to execute a sequence of motor actions (e.g., get out of my chair and move something that needs moving) or to plan out how to achieve some goal.
If you felt like you could have gone longer, then I'm sure you could have gone longer. Two things worth noting, however:
First, it's good to have a minimum amount of time in mind for a meditation session, and stick to it. You can always stay seated after your timer goes off. Without a firm minimum, it's very easy to stop as soon as you get fidgety. Speaking from my own experience, sitting through fidgetiness has been the immediate precursor to some of my most meaningful progress in meditation.
Second, consistency is more important than intensity. My (personal, inexpert) recommendation is to choose a time that you can manage every day, and stick with it. Don't over-commit, or you may get burned out. For me, 20 minutes is about right. YMMV.
For the mental aspect, a good starting point is the audio session Alan Watts Teaches Mediation. http://www.youtube.com/watch?v=_tYENNBA0cA