A newbie question

There are no dumb questions here!  I have to say I never really thought about pacing - I just run the best that I can.  I suppose you could monitor your heart rate.  Or use the RPE scale (rate of perceived exertion).  I used to throw up after races too, but not anymore! 

I guess use your best judgment and consider how long you need to run when deciding how fast you should go.  In a typical week, I do 3 run workouts.  One long, slow run where I'll be able to run as far as I want without feeling dead, one interval workout with sprints (this builds speed), and one short-ish run at a higher level than the long run. 

I guess we'll wait and see what others have to say

I suppose I should have read this thread BEFORE the one about Keeping up with the Tri-Joneses...

I base my pace off my HRM - however, I can also do it with just my watch and my normal route.  I'm luck that the trail I typically run is marked every .2 miles, and by some quick mental math, I can figure out my pace and if I'm where I should be.  I am starting to figure out my RPE with my HRM, and I don't have to look as often to stay within the zones I want to stay in.  Sunday is my long run: 10 miles at (roughly) 10 minutes per mile - this pace has been falling recently, as my HR is staying well within my zone (must be getting more fit!)  Tues: 5 miles at my 10K race pace, with 6-8 hill repeats after I'm done.  Thur: 5 miles at just under 10K pace, with several Fartleks thrown in (basically, I sprint past every walker and jogger that I pass, or just stride out 1/5 mile) for speed.  Friday is my off day, although I sometimes go run 5K as hard as I can.

To help build leg strength, I lift MWSa, and anytime I bike somewhere, I try to take the hilliest route so that I can build more leg strength.  Running and biking hills has really helped my running.

On your first tri, your run pace will be slow coming off the bike (unless you do plenty of bike-run bricks before the race).  Don't go all-out right away; your brain will know something's up, but it'll take a bit for your legs to figure it out.  Once that happens, you'll build into your typical 5K pace quick enough (for a sprint).  If you can afford it, get a heart-rate monitor and wear it for a couple of 5K or 10K runs, so that you can figure out your 'race pace', and then when the sprint tri comes around, you'll know what you can handle.

Intervals.....I do one of a few things.  You can use the treadmill, warm up with a short run, then do sprints for 30-60 sec, then jog to recover and repeat!  Or I go to the track and run either 200m or 400m fast and jog a lap to recover (and repeat).  Or I do hill repeats - I go to a steep hill, run up, and jog down - and repeat until I'm dead tired. 

Intervals help with speed, long slow runs help with endurance.