If you want to reseed, then the best time to do that is in the last summer/early fall. If you want to put sod down, you can do that any time. Most people wait until spring.

The reason you had trouble is your grass is most likely either fescue or rye. Those grasses do not spread like Kentucky bluegrass does. KBG is a full sun type grass, so consider the presence of tall trees, fences, and buildings in your planning. Fescue can tolerate more shade than KBG so that might be why you have it.

If you decide to go with fescue or rye, you might need to continue reseeding it every fall for awhile to make it as dense as you want.

When you get a lawn established, follow these three rules...

Basics of Lawn Care

After reading numerous books and magazines on lawn care, caring for lawns at seven houses in my life, and reading numerous forums where real people write in to discuss their successes and failures, I have decided to side with the real people and dispense with the book and magazine authors. I don't know what star their planet rotates around but it's not mine. With that in mind, here is the collected wisdom of the Internet savvy homeowners and lawn care professionals summarized in a few words. If you follow the advice here you will have conquered at least 50% of all lawn problems. Once you have these three elements mastered, then you can worry about weeds (if you have any), dog spots, and striping your lawn. But if you are not doing these three things, they will be the first three things suggested for you to correct.

Watering
Water deeply and infrequently. Deeply means at least an inch in every zone, all at once. Infrequently means monthly during the cool months and no more than weekly during the hottest part of summer. Do not spread this out and water for 10 minutes every day. If your grass looks dry before the month/week is up, water longer next time. If that does not work, then you might have to water more than once per week during the summer's hottest period. Deep watering grows deep, drought resistant roots. Infrequent watering allows the top layer of soil to dry completely which kills off many shallow rooted weeds.

You will have to learn to judge when to water your own lawn. If you live in El Paso your watering will be different than if you live in Vermont. Adjust your watering to your type of grass, temperature, humidity, wind, and soil type. It is worth noting that this technique is used successfully by professionals in Phoenix, so...just sayin.' The other factors make a difference. If you normally water 1 inch per week and you get 1/2 inch of rain, then adjust and water only 1/2 inch that week.

Mowing
Every week mulch mow at the highest setting on your mower. Most grasses are the most dense when mowed tall. However, bermuda, centipede, and bent grasses will become the most dense when they are mowed at the lowest setting on your mower. In fact there are special mowers that can mow these grasses down to 1/16 inch. Dense grass shades out weeds, keeps the soil cooler, and uses less water than thin grass. Tall grass can feed the deep roots you developed in #1 above. Tall grass does not grow faster than short grass nor does it look shaggy sooner. Once all your grass is at the same height, tall grass just looks plush.

Fertilizing
Fertilize regularly. I fertilize 5 times per year using organic fertilizer. Which fertilizer you use is much less important than numbers 1 and 2 above. Follow the directions on the bag and do not overdo it. Too much is better than too little*.

At this point you do not have to worry about weed and feed products - remember at this point you are just trying to grow grass, not perfect it. Besides once you are doing these three things correctly, your weed problems should go away without herbicide.

* This used to read, "Too little is better than too much." Recent test results show that you cannot get too much organic fertilizer unless you bury the grass in it.

Many people have trouble growing grass for a few reasons. You said you tried growing grass last summer. If you seeded in early summer, that was your first mistake. Cool season grasses are best seeded in late summer, early fall (timing depends on local climate). Early spring is also an option, but it isn't as good as the late summer/early fall seeding. You will have to keep the dogs off new grass for at least two months, but your results would be better if you keep them off till the next spring. New grass is fairly resilient, but doesn't take to well to traffic, especially active dogs. Once you get the timing down, the number one reason people fail at growing grass is improper watering. Grass seed needs to be continually moist until you see green all over, then it still needs frequent watering till mature. Another thing is for great grass you need great soil. Test your soil this spring so you can improve it prior to seeding. Use a reputable lab (www.loganlabs.com).
Seed selection is important. I don't quite agree with Dchall, in that the type of grass is why you failed, but in Colorado, Kentucky bluegrass is probably the best choice as it tolerates cold better, and spreads to fill in voids. If you have a lot of shade however you will have to go with TTTF or fine fescues.

Here's my advice for what to do. When the ground has thawed, send your soil sample to the lab I mentioned above. When results come back, add amendments throughout the spring and summer. Add organic matter to your soil as your budget allows. You say you have bare dirt. You might want to cover it with mulch to prevent erosion, improve the soil, and so you can deal with any weeds that pop up and make sure they don't seed. In mid summer you should eradicate all weeds, and continue to do so until you seed. When you seed remove the mulch, seed bare dirt, roll the seed, and topdress (optional but I feel it gives better germination and prevent runoff to a degree). Water three times a day till germination, then start cutting back on the watering every week or so. Cut the lawn when it hits about three inches (cut to 2 inches). Again, this is very basic. Seed selection is another topic unto itself. Another thing to consider is planting grass this spring just to get coverage, with the intent to kill it all in the summer. You should use a fast germinating/establishing grass for this like TTTF or annual rye.