Coaches of youth basketball teams in Northern Virginia may register in advance through tomorrow for the Fifth Annual Youth Coaches Basketball Clinic, to be conducted at Paul VI High School in Fairfax on Oct. 31. Advance registration costs $12. After tomorrow, the fee will be $20. Fee includes lunch, and door prizes will be awarded. For more information, call Ed Grimm at 273-3532 or Brian Doyle at 938-8345.

Find out about law careers at a free workshop at 7:30 p.m. tonight at the Arlington County Central Library. Bettina Lawton, practicing attorney and former president of the District of Columbia Women's Bar Association, is the featured speaker. The Central Library is at 1015 North Quincy St., Arlington. For details, call 284-8181.

Children and their parents can help build the "World's Largest Scarecrow" from 10 a.m. to 5 p.m. Saturday and Sunday at the Pet Farm Park in Reston. Part of the admission fee will benefit UNICEF. From 2 to 5 p.m. Sunday, children also can meet Loretta Long, who plays Susan on "Sesame Street." The finished scarecrow will be raised on Sunday. Pet Farm Park, a zoo that permits visitors to touch approachable animals, is at 1228 Hunter Mill Rd., Reston. Admission costs $4 for adults, $3.50 for children ages 2 through 12. No charge for children younger than 2. For more information, call 759-3636.

All young witches, ghosts and ghouls (and their parents) are invited to register to march in costume in the Vienna Halloween Parade Wednesday. Children must be registered in advance, accompanied by an adult, in the children's section of Patrick Henry Library, 101 Maple Ave. Sign-up times are 11 a.m. to 1 p.m. Saturday, 1 to 4 p.m. Monday, and 3 to 7 p.m. Tuesday. For more information, call 281-1333.

Enjoy autumn in the free 10-mile Fall Foliage Hike on Saturday, sponsored by the Arlington County Department of Parks, Recreation and Community Resources. The hike will start at 9 a.m. at the Gulf Branch Nature Center, 3608 North Military Rd., follow the Potomac River on both sides, and include the Potomac Heritage and the C&O Canal trails. Approximate ending time is 4 p.m. The hike is open to teens and adults, and reservations are required. Call 558-2340.

The Fairfax County Department of Animal Control will mark dogs or cats with owners' Social Security numbers at a tattoo clinic from 10 a.m. to 4 p.m. Sunday at Fair Oaks Public Safety Center. Tattooing is painless and will protect pets permanently from being lost without identification. The process requires no tranquilizers or anesthetics and takes a few minutes. Once tattooed, a pet becomes registered with a national 24-hour lost pet telephone service. Animals must be at least six months old to be eligible, and owners must show a current rabies inoculation certificate. Clinic services cost $5 in advance or $10 upon entry. Fair Oaks Public Safety Center is at 12300 Lee-Jackson Hwy. For details, call 830-1100.