Fertilize :
New Jersey: Fertilize in late may, early september and 1st week of november. avoid fertilizer during hot summer months. These 3 times are the most important for us in New Jersey.

Grubs:
To determine whether or not there is a significant number of grubs to warrant control practices, remove a square section of lawn 6 inches by 6 inches and 4 inches deep. Turn the section of lawn unto a flat surface, use a trowel to break up the soil, and place any grubs you find in a cup. A healthly lawn can usually tolerate 8 to10 grubs per square foot without showing signs of distress.
Most conveniently turf/soil plugs are sampled with a standard golf course hole cutter (4.25" diam ~ 0.1 ft²).
Damage thresholds vary considerably with grass species, management type, and climatic conditions. The better maintained the turf and the more extensive the root system, the higher are the damage thresholds.
Among the coolseason grasses, tall fescue is the most grub tolerant species whereas perennial rye grass is the least tolerant.
If a lawn is being dug up by skunks, raccoons, or crows, particularly in March through May or in September or October, or if moles are creating a network of tunnels under the grass, it is likely that the lawn has a significant population of grubs which the animals are feeding on.

Due to the White Grubs' (WGs) tunneling activity, infested turf feels spongy underfoot and can be pulled up like a carpet, exposing the C-shaped WG.
If soil sampling has revealed high WG populations, treatment may be necessary. This curative control approach works best if applied while the grubs are still smaller (i.e., mid August to early September). Once the grubs have reached the 3rd larval stage, they are much harder to control.
Spring applications (late April through May) are generally the least effective and rarely justified because the grass can outgrow most grub populations.

Chemical control - curative:
Insecticides available for curative WG control include the organophosphates trichlorfon (Dylox(R), Advanced Lawn 24 Hour Grub Control), diazinon (Diazinon(R); not for golf courses, sod farms, turf areas > 1 A), and chlorpyrifos (Dursban(R); only on sodfarms), and the carbamate carbaryl (Sevin(R)). For late applications and thatchy lawns, trichlorfon is the usually the best choice.

Chemical control - preventive:

Advanced Lawn Season-Long Grub Control) and the molt-accelerating compound halofenozide (MACH 2(R), GrubEX). Due to their long residual, imidacloprid and halofenozide can be applied as early as May and June, respectively. If applied that early, various other insect pests may also be controlled (billbugs, annual bluegrass weevil, greenbugs; halofenozide also cutworms, sod webworms).
If WG are the primary targets, the optimal application time for imidacloprid and halofenozide is June/July when the female beetles are laying eggs. As the larvae grow, they become less susceptible to these insecticides.
Scott's GrubEX and Bayer Advanced Lawn season-Long Grub Control will contol grubs without killing beneficial earthworms.

Biological control:
Presently available products containing the insect parasitic nematode species Heterorhabditis bacteriophora (e.g. HeteromaskTM, GrubstakeTM Hb), Heterorhabditis megidis (e.g. Nemasys(R)H, GrubstakeTM Hm), or Steinernema glaseri can provide very good control of Japanese beetle, but are not effective against oriental beetle, Asiatic garden beetle, or European chafer grubs.

Mowing:
Studies show that this causes less stress to the grass plant than heavy, infrequent cuttings. The general rule is cut no more than 1/3 of the grass blade at any one cutting. Otherwise the grass is deprived of too much of its energy-storing foliage and has to devote its resources to rapidly replacing the foliage at the expense of root development.

Clippings do not cause thatch.
Leave Clippings To Fertilize - When you leave the clippings to decompose on the lawn as you mow all season, they provide 25% of your lawn's annual nitrogen requirement.

Leave Clippings To Mulch - Left on the lawn, grass clippings serve as a temporary mulch, blocking the evaporation of moisture from the soil.

Leave Clippings To Save Time - It takes 30% less time to mow a lawn and leave the clippings than it does to go to the trouble of collecting and bagging those clippings.

Don't mow grass with a dull mower blade.

Some sites say to mulch with your last mowing. Mow right over a 1/2 inch or so of fallen leaves for your final mowing in the fall. With the help of soil organisms they will decompose among the grass blades over the winter, adding organic material to the soil.
Others, say not to. (ExtremelyGreen.com/lawncareguide.cfm) yardener.com/MowingTheNorthernLawn.html

Mowing Height:
Tall Grass Has Fewer Weeds - Routinely mowing northern turfgrasses to a minimum of 2 inches high reduces weeds 10 fold over mowing 1 inch high because the longer blades block the sun that ever-present weed seeds in the soil need to germinate. Set the mower at about 1 1/2 to 2 inches (for Bluegrass-Fescue lawns) then gradually raise it to 3 inches by early June and for the rest of the season.

Summer:
3-3.5 on non irrigated.
2.5 to 3 on irrigated.
tall fescue 2 - 4"
fine fescue 11/2 - 2 1/2
Bluegrass 2 - 3
RYE  1 1/2 - 2 1/2
(some sites show lower heights, but higher heights reduce weeds)

Spring 1.5"
Fall 2.5" final 2"

Last several cuts of the season, start cutting lower (down to 1 inch for perennial ryegrass and fine fescue, 2 inches for kentucky bluegrass and tall fescue).

See: Grubs at massaudubon.org
An Integrated Approach to Insect Management in Turfgrass: White Grubs, Rutgers Cooperative Research and Extension Fact Sheet (FS1009) at somerset.nj.us