I suggest seeding in late August or early September. Do a soil test now and get recommendations on lime and any other nutrients your soil needs. You can make amendments this spring and summer to help prepare. Lime, if it's still needed, can be applied every 90 days during the growing season. You could work on killing weeds now or wait until July if you want to kill everything for a fall renovation. You may just want to do an overseeding. If you want to work on weeds now, use a pre-emergent when the forsythia blooms. Use an amount that will wear off by the time you want to seed (read the directions). Use a broadleaf weed killer later in the spring when the weeds are actively growing. If you want to work on weeds later, just mow them this spring and then use Roundup to kill everything in July. Water lightly each day to encourage weed seeds to germinate and a few weeks later kill them again. If you don't want to kill everything but just want to overseed, use selective weed killers this spring and summer as needed and pay attention to how long you must wait until you can seed (read the directions). Sow seeds and water lightly and frequently, gradually decreasing frequency and increasing the amount as the grass comes in. As far as fertilizer, you could do an application in late May, then an application at seeding in August/September (starter fertilizer), then another application (normal fertilizer) in October, and a high nitrogen one after the grass stops growing but before the ground freezes (maybe around Thanksgiving). Do not fertilize in early spring. Keep any lime applications two weeks from any fertilizer. Straw would go on top of the seeds when you seed. All this is assuming you have a cool season grass. What kind of seed will you be using? Are you using good lawn practices for mowing and watering? Don't cut off more than 1/3 at a mowing. Water deeply and infrequently. When you seed, do not use a weed and feed fertilizer as it will keep grass seeds from germinating. In general, use weed killers for weeds and plain fertilizer for fertilization instead of a combination product.

You can apply lime anytime. I would recommend staying away from weed and feed products, buy fertilizer and weed control products and apply them separately. Spring is a poor time to seed, the weeds will happily germinate right along with your seed. Tough it out until fall if you want a nice lawn. There are 4 crucial elements to seeding: seed quality, seed to soil contact, water and soil temperature. A few weeks before it's time to seed, Round-Up everything so you can get rid of all the weeds. When it's time to seed, cut the now dead weeds as low as your mower will cut. Get ahold of a power rake/dethatcher and run it over the entire area to pull up all the thatch/dead grass. Pile up the thatch in a corner somewhere. Apply your seed of choice with a rotary spreader, then immediately startup fertilizer. Get the thatch you piled up and start spreading it on top of the seed to cover it. The whole thing will look like crap, this is normal. Now water, you only need to keep the top of the soil moist, no deep moisture needed yet, so water light and frequent. Do not let the seed dry out. Good quality tall fescue will begin to germinate as soon as 4 days in 80-85 degree weather. Keep the seedlings well watered, reduce watering frequency and increase watering length as the seedlings mature. Cut when the grass reaches 3.5 inches. To avoid weed issues the following year, apply pre-emergent every spring and post-emergent as needed to whatever breaks through before it gets a chance to produce seed.

In regards to beckyinrichmond's recommendation above to fertilize in May, NCSU recommends not fertilizing after March 15th due to increased probability of brown patch, which is a major issue around here. I recommend going through their site, tons of great resources from our state university. http://www.turffiles.ncsu.edu/

Good point about brown patch. Nitrogen can encourage lush growth which is more suspectible to brown patch. You want to avoid fertilizer in early spring because then you're pushing top growth at the expense of the roots. But by late May the flush of spring growth is over and grass could use a boost to get through the summer. Don't fertilize in hot weather as that is stressful. So late May/early June is when the grass could use some fertilizer and it's before summer heat settles in. That is also the time for brown patch. I suggest cornmeal in May to serve as the fertilizer then and to help protect against brown patch. I think it's 10 lb/1000 square feet as a preventive, 20 lb/1000 square feet if you're trying to cure it. Also, Serenade is a biofungicide that can help protect against brown patch if you use it consistently throughout the season.