NEW YORK, JULY 2 -- The Dow Jones industrial average kicked off the second half today with an 18-point advance in light and generally dull trading.

Only a handful of ''deal'' stocks -- such as General Instrument and Kay Jewelers -- drew attention in the cash market, traders said, and small fluctuations in stock index futures presented little opportunity for arbitrage.

Even so, market-watchers were generally pleased with the way the market shrugged off a falling dollar throughout the day -- the first trading day following the unprecedented unification of East and West German currencies, which occurred officially at midnight on Sunday -- as well as a soft bond market in early trading tied to the latest report by the National Association of Purchasing Management. Bonds also did not lend much support to stock trading.

At the close, the Dow stood at 2899.26, up 18.57, but advances managed to edge declines only in the last minutes of trading by 779 to 736, having trailed them by a 7-to-6 or greater ratio all day. Volume was 130 million shares.

''It was the kind of day that the bears hate,'' said analyst Donald Selkin at Prudential-Bache. ''Volume is crummy, breadth is negative for the most part, yet the market goes up.''

Electronic-components maker General Instrument celebrated the Fourth of July early, rocketing up 8 3/8 to 45 5/8 after a delayed opening following a report that it has held talks with Forstmann Little and Co. about a leveraged buyout valued at about $40 per share. The deal was later announced, and General Instrument closed up 8 7/8 at 45 1/8 in heavy trading.

N.V. Philips dropped 7/8 to 16 7/8 after the company projected a loss of more than $1 billion for the year, including a restructuring that will involve trimming 10,000 people from payrolls worldwide.

McDonnell Douglas's battered stock gained 1 5/8 to close at 38 1/8 after a San Francisco buyout firm acquired the company's computer maintenance and distribution system for $65 million.

Dow components' early leadership generally followed through with conspicuous gains by the close. General Electric rose 1 1/4 to 70 1/2, while IBM gained 1 to 118 1/2 and Procter & Gamble added 1 1/8 to 88 1/4.

Among broad stock indexes, secondary measures lagged the blue-chip averages -- typical of program-driven gains in the glamour stocks, traders noted. The Standard & Poor's 500 was up 1.52 at 359.54, the NYSE Composite up 0.74 at 196.22, the Value Line up 0.36 at 286.99, the Amex Market Value down 1.07 at 360.14 and the Nasdaq Composite down 0.25 at 462.04.