It takes a very special deal to get consumers up and waiting outside stores in the cold, hours before the sun rises.

Cue the Black Friday door-buster. The limited-quantity, limited-time deals typically sell out within minutes of the store opening. About 6% of shoppers plan to arrive at stores before midnight, and nearly 40% by 6 a.m., according to a survey from the National Retail Federation. You have to be just a little bit crazy, says Sok Verdery, the chief executive of CouponShack.com, a deal and coupon site.

Bear in mind, too, that many stores have enhanced safety precautions to make sure no shoppers are injured in their quest to get one of the coveted deals. The result: a long wait. Wal-Mart, where Black Friday crowds trampled and killed a store worker last year, plans to keep stores open 24 hours on Thanksgiving Day and create separate lines for each of its door-buster items. Best Buy is offering tickets for a shot at door-buster deals as early as 3 a.m. in some locations, which can be redeemed once the store opens at 5 a.m.

Before you get swayed by the low, low prices in today s circulars, read our Black Friday shopping guide

Based on rumored deals and retailer-confirmed ads available earlier this week, Verdery and other deal hunting experts liked these three categories for early Black Friday sales:

1. Apple products

At publication time, Apple had yet to release details of its one-day Black Friday shopping event beyond a promise of free shipping, but that doesn t matter. This is the only sale Apple has, says Dan de Grandpre, the chief executive of sale tracking site Dealnews.com. Be sure to check it out. Tech blogs have speculated discounts could run as high as 30% on laptop computers and MP3 players.

2. 42-inch HDTVs

TVs have hit a sweet spot in pricing at around 42 inches, Verdery says. At that size, you ll find both plasmas and LCDs, which leads to plenty of competition during the regular sales cycle. Black Friday is no exception. Sears has the Panasonic Class 42-inch 1080p Plasma HDTV for $650, a $350 (35%) discount.

Netbooks

It s likely be a killer year for netbook deals, says Andrew Eisner, director of content for Retrevo.com, an online electronics marketplace that offers user manuals and consumer reviews. Check circulars carefully Thursday for deals like those expected on the 10-inch Acer Aspire One Intel Atom N270. Earlier this week, prices were a rumored $197 at Sam s Club and $200 at Office Depot , which would knock $100 or so off the original $300 purchase price. (See our tips to buy the right netbook