Be mindful when packing
Think about the activities you'll be doing and the weather when styling outfits beforehand and then pare down to the essentials. Style outfits that utilize mixing-and-matching pieces so that you can pack lighter. For instance, I have a trip to the city coming up. It's a seven day trip, so I've calculated that I will only need to bring along four full casual outfits, one formal, plus pajamas and workout clothes. Utilize your hotel's laundry services so that you can re-wear items of clothing.
Read blogger travel guides in lieu of guide books
Guide books tend to point you in the direction of the tourist hot spots and away from the places that are actually enjoyable and interesting. Forgo these guide books and use blogger travel guides instead. Blogs like Design*Sponge, Goop, and Tory Burch offer great city guides which point out the lesser known, locals-approved places you should visit in cities like New York, Paris, and more. Bloggers like Julia Engel are great at providing unique ideas for travel.
Utilize travel deal sites
There is no good reason not to utilize these kinds of websites. Never book a flight or a hotel without consulting a good deal site. For hotels, I absolutely adore Tablet and for flights, Expedia and StudentUniverse are always good.
Create a cheat sheet
I've mentioned before the idea of creating destination packets for each place you plan to visit. This is a great way to have ideas about what you want to do, see, eat, etc. but not have to actually plan out your days too stringently. I like to make long lists of restaurants, stores, museums/galleries, and other places that I find interesting so that I have a reference point.
Download a good transportation app
HopStop used to be my go-to, but now that they are no longer around I recommend the app Transit which makes navigating any subway system super easy. That way, you don't have to look like a newb carrying a map or asking for directions.