Getting around – whether you fly or drive, if you want to visit more than just the “Mall,” stay at a hotel that has a metro in the near vicinity. That will make getting around DC and the outlying areas easy, more economical, and less stressful. (The Mall is a long line of Smithsonian Museums)
Plan for the weather – No matter when you go, there will be times when you should be inside where it’s cool, dry, etc. vs. visiting monuments and memorials. Check the weather forecast before your vacation and be flexible.
Getting the most out of your trip – be strategic when planning your itinerary. I group places that are close together so my fiancé and I aren’t spending a lot of time traveling from one attraction to another.
Best way to see most monuments and memorials – take a hop on/hop off tour. There are three companies that offer these tours in DC and tickets can be purchased at Union Station. One word of caution, don’t stay on the tour bus and complete the whole circuit and then go back to the attraction(s) of your choice. If you do, you’ll waste valuable time. Also, be sure to check on times the tours begin and end operation for the day as those vary depending on the time of year.