Fertilize and overseed

and your location is?

Jim wrote in news: snipped-for-privacy@bellsouth.net:

Victoria, British Columbia, Canada.

You should do them at the same time. Use a starter fertilizer. You can do it now, but the best time for seeding is in the Fall. If you have any reasonable size, I'd recommend renting a slit seeder. They generally go for about $60 for 4 hours, will save you a lot of work and get the seed into the ground where it will have a good germination rate. Some people buy $75 worth of seed and just sprinkle it around, where little of it actually grows. Also, make sure you use a good and proper seed.

now that we know your location we also know you are not subject to intense hot summer sun as areas to the south of you are. it is that hot intense heat that kills most seed just as it begins to germinate and that's why fall seedings have produced better yields.

I second the recommendation you rent a slit seeder because getting the seed into the ground provides a dramatic improvement in the germination rate. The cost of the seeder can be recovered in the area of improved seed germination. An accompanying lite application of a starter fertilizer during an over seeding of an existing lawn will improve the growth rate of new grass. However, consideration for the grass type and its nitrogen requirements needs to be taken into account before adding anymore nitrogen to the existing lawn.