Since you're asking about seeding in the spring, I presume you seeded in the spring last year. Spring is almost the worst time of year to start grass seed. Summer is the only worse time. Late fall is the best time and it goes downhill from there. I would strongly suggest sodding this time of year. The sod goes down and you have an instant lawn. Depending on how big your bad parts are, you can keep the existing good grass and drop pieces of sod in the bad spots. Sod can be chopped to fit odd shapes and curves. For a small area, it should work for you.

Religious about watering: Does that mean every Sunday or only on Christmas and Easter? Usually that means you watered too frequently. I'll post my paragraph on watering at the bottom of this.

The two most popular northern lawn grasses are fescue types and Kentucky bluegrass. Fescue is a bunch grass that will not spread. The only way to fill thin spots is with more seed. It is not unusual to have to reseed thin spots every fall. Fescue grows in full sun and in partial shade. Kentucky bluegrass is a sod forming grass that will spread to fill in thin spots. It grows in the full sun and thins out in the shade. Many people have a lawn with trees, fences, or whatever that casts shade in the yard. A mix of KBG and fescue is popular to keep the grass looking pretty good everywhere.

If you still have crabgrass, then it is not crabgrass. Crabgrass is a summer annual plant that always sprouts from seed in the spring and dies in the fall. You might have orchard grass, dallis grass, or barnyard grass. They are often mistaken for crabgrass. Those must either be pulled out or sprayed out with Grass-b-Gon or Round Up. Spot spray the weeds carefully because grass killer will kill your good grass, too. Whatever it is, get rid of it before you sod or seed.

Let us know which way you decide to go (seed or sod) and we can give you some tips to make it go right for you. There are some blunders you can make, so let's talk first.

Watering: Deep and infrequent is the mantra for watering. This is for all turf grass all over the place. Deep means 1 inch all at one time. Put some cat food or tuna cans around the yard, and time how long it takes your sprinkler(s) to fill all the cans. Memorize that time. That will be the time you water from now on. My hose, sprinkler and water pressure takes 8 full hours to fill the cans. Your time will likely be less. I like gentle watering. As for watering frequency, that depends on the daytime air temperature. With temps in the 90s, deep water once per week. With temps in the 80s, deep water once every 2 weeks. With temps in the 70s, deep water once every 3 weeks. With temps below 70, deep water once a month. Note that you have to keep up with quickly changing temps in the spring and fall. This deep and infrequent schedule works in Phoenix and in Vermont, so it should work for you. The reason for deep and infrequent is to grow deeper, more drought resistant roots and to allow the soil to dry completely at the surface for several days before watering again. If it rains, reset your calendar to account for the rainfall.