A successful day of sightseeing is finding the right balance of sightseeing, spontaneity, relaxation and feeling like a temporary local.
I suggest waking up early in the morning, have breakfast and head out early to beat the tourists who slept in late. Of course there will be days when getting up early is tough because you may be tired from traveling or sightseeing the previous day.
This is why you should never plan too much for one day. Also allow yourself ample time during the day to be spontaneous and see where the wind takes you. I've come across a flag throwing demonstration, marching band, and the usual street performers while traveling. It's the little things like this that are most memorable.
2. Avoid Long Lines
I highly recommend you to buy tickets online a few weeks before your trip for popular tourist attractions that are known to have long lines during the busy season. There may be an additional small fee but the price is totally worth not wasting precious time standing in line just to buy tickets.
For instance, I love arriving to the museums early in the morning before it becomes too crowded with tour groups and tourists. You can enjoy your favorite paintings and artifacts hassle free when you first arrive. I suggest splitting your museum visit with a lunch break depending on the size of the museum. I prefer to only visit one museum per day taking my time to fully enjoy the exhibits. With so many museums to see, I recommend choosing a few and saving the rest for another trip to avoid museum overload. This is always a good excuse for a future visit.
3. Have A Loose Itinerary
I suggest having no more than two major things planned per day in order to fully appreciate your time for each place you are visiting. Travelers often try to cram too many things into a few hours rushing from place to place without fully appreciating the present moment. It's best to slow down and totally immerse yourself for each thing planned. Some of the most memorable moments often occur when you just go with the flow.
It's also best to have some downtime to relax and soak in the culture. I'm big on relaxing at local coffee houses with a beverage and something light to eat between meals. I enjoy this time people watching and researching things to explore on the off beaten path away from the touristy areas. This is also a great time to recharge your cell phone battery and freshen up.
4. Take A Break From Sightseeing
Take a break from sightseeing to relax while still enjoying the sights. You can always find somewhere interesting to hang out without having to go back to the hotel. For instance, enjoy a picninc at the Eiffel Tower, A slice of pizza in The Piazza del Campo in Siena, Italy, sit on a bench in front of the fountains at the Burj Khalifa in Dubai, enjoy the majestic views of the Jungfraujoch in Switzerland, wonder at the site of the Blue Mosque in Instanbul. These are a few examples of how to take a moment and soak in the culture while relaxing in the middle of sightseeing.
5. Become A Temporary Local
Always take time to talk to the locals during daytime hours in an open area in a family friendly environment. No matter what country I'm visiting I always manage to become a temporary local and adjust to their way of living for a few days. It is the best history lesson that will offer the most amazing experience free of charge. You can also attend a religous service or go to the library to witness first hand the local culture.