I've lived in the city for 20 years and the Mall is where Gidget does most of her walks and bikejoring. I feel entirely safe walking there alone with Gidget, day or night. It's well patrolled by the U.S. Park Police and lighting was greatly improved around the Lincoln Memorial after some incidents a few years ago.

The Smithsonian Museums do not have x-ray machines. They do hand inspections of your bag(s). Pretty cursory, in my experience. You hold it open usually and they peak in -- possibly with a flashlight. I've never had a knife or pepper spray or anything else confiscated at a Smithsonian and I always have those with me -- usually in a rucksack. I often duck into a Smithsonian -- usually the castle -- to use the restroom. Just don't carry a big knife and don't have it or pepper spray visible at the top of the bag. If you are going to bring a knife, bring a little one.

The Smithsonians are open until 7:30p during the summer.

Here's what I would recommend for summertime Smithsonian touring: carry a light rucksack. Have in it or carabinered on it: water, glasses, suntan lotion, hat, compact umbrella (unless the forecast rules out afternoon thunderstorms), light windbreaker, energy bar, Doug Ritter's e-PICO light, cotton bandanna. I'd also be packing a little Surefire light, but that's me: I'm a flashlight freak.

There is food on the Mall -- kiosks and carts which sell drinks, hot pretzels, hot dogs and ice cream. There's a McDonald's at Air & Space and nice cafeterias or cafes in the Indian Museum, American History Museum and National Art Gallery.

Do not carry all your cash or credit cards in one place.

Pickpockets target tourists. If you have more than one credit card, maybe leave one in the trunk of your car. Do not let your bag(s) out of your sight, ever.

Not assuming that you might but will go ahead and caution: Do not bring a gun into DC. Doesn't matter if it's legal where you live, it's not legal here. They will throw you into jail in a nanosecond and the gun will be confiscated and destroyed. The handgun law has loosened up a bit but is still very strict and I don't know that it gives any leeway to nonresidents. You certainly do not want to be caught with one around the Capitol, White House or the Mall.

Have you booked a hotel? Look for something close to the Mall. There are reasonable options. If you are going to stay in a suburb just know that the morning rush is from 7-10:00a (8-9:00 being the worst) and 3-7:00p (3:30-6:00 being the worst). Tuesdays-Thursdays are the worst traffic jams. Monday and Friday traffic is lighter, especially in summer. Driving and parking are easy on weekends -- unless there's a big protest, parade or marathon. Check The Washington Post for such events. If you are going to be concentrating on Smithsonian Museums,the memorials and the White House then it is advisable to stick with the Metro.

Also Google the "Tourmobile."

There are public parking garages within a couple blocks of the Mall. If you don't mind paying, that is an option. Union Station has a public parking garage and is a major stop on the subway's ("Metro") Red Line. You can also catch at Union Station some tourist transportation: Tourmobile, Old Town Trolley, DC Duckmobile or the British-style two-story bus tours by American Heritage. They have different packages. The narrated Tourmobile allows you to get on and off during the day and can take you to Arlington National Cemetary and Mt. Vernon if you buy those packages:

http://dc.about.com/od/walkingtours/a/5BestTours.htm