I work at a hotel front desk (hence the downtime for writing this!) and not only have I come in contact with the angry guests but the happy ones too.

Some advice for booking a hotel:

Make sure you have specific directions to get there BEFORE you leave your house. If you feel uncomfortable, call the hotel and ask them once you get into the area, what is the best way to get to their hotel.

Locals always seem to have a better, more savvy way of getting around (Locals are Great Tourist trip advisors!!). And from experience, from answering these questions so often, front desk clerks have the best insight to what works and what doesn't because lord knows I have heard all the good  and bad things people have done while trying to get here! (Going up the wrong ramp, turning getting stuck on the curb-like medians, driving to PHILADELPHIA when they should have been in Lancaster...the list goes on)

Looking at the Hotel Reviews/how to react when there are problems:

Sure you want to know what other people thought about their stay and of course you want to be comfortable when you are away from home, but just remember, it's not your home but most reputable places will go above and beyond to help you feel at home.   Sometimes hotels have renovations, the end results are usually fantastic and sometimes you book there not knowing that. The best way to approach that situation is by asking the front desk or a manager on duty what is happening. Questions like "what time do they start construction in the morning?" "Should I worry about being awakened by these changes?" If there are problems with the room and you are unsatisfied, the best way to fix it is to ask for a manager politely, no matter how angry you may be, anger doesn't usually get the job done in these situations. The best thing to do is to ask how the property can fix your complaint. Things like, noise from construction is a HUGE problem to some guests and the best thing to do is to offer a rate decrease for their stay or to offer to contact another property to accommodate them. By asking for these two options calmly you may get some great things out of your stay, like complimentary stays in the future and more. I know that if you are staying in a GREAT city like Pittsburgh you will want to come back and believe me, the hotels WANT your return business.
Dirtiness of the rooms and Lobby are a whole another story. You know when a room and property has been taken care of properly over the years. Finding trash or dirt in a "Clean" room is unacceptable. Politely tell the hotel you wish to stay somewhere else and address this towards a manager. There is just no excuse for uncleanliness, no matter how low the rates are.

A great rule of thumb to live by when you are a guest at a hotel is patience. Hotels have ‘rules' (for lack of a better word) to help assure guests proper service. For instance, check in time and check out time. They are in place not to aggravate you, but to assure you that your room is ready and the establishment can guarantee you the best stay possible

More to come, please leave comments/questions so I can also address them!