First, keep in mind that your goal is not to evaluate the truthfulness of individual reviews, it is to find a good place to stay. There are thousands of reviews across hundreds of places. Analyzing individual reviews is a fools errand, unless you actually know the reviewer or noticed the reviewer seems to agree with you in general.
Here is a small description of what I do to decide on a place:
0.a. Price range.
Obviously, it's got to fit your budget, but also, don't forget that reviews are relative to the expectation of the visitors. You will find a lot of places with fantastic ratings for a thin bunk bed in a dorm room and a dirt cheap price, while a poorly reviewed high end hotel room would exceed the wildest expectations of the backpacker crowd. Limiting your search to your price range will save you a lot of time and prevent a lot of disappointments.
0.b. Location: check on the map what the distances are to the major attractions and make sure you convert these in hours and minutes. Zoom can sometimes trick you. If proximity to a specific place is important to you, go to Google map and get directions. Google's time estimates are usually pretty good and take into account different types of transportation. You don't want to end up with an hour long commute or worse just because the place "looked close enough". That can really ruin your trip.
0.c. Photos analysis:
Does the place look like the kind of place you would want to stay at? Hotel photos provide a upper threshold for quality. If the photos look bad to start with, never mind the reviews, it's rarely going to be better than the pictures.
Next, pay attention to the quality of the bedding and bed accessories. The bed & bed linen are often the single most expensive furniture items in a room and prices vary widely. If the cover looks thick and nice, the bed inviting, it usually means that the hotel spend serious money on guest comfort.
Look at the TV. Is it a flat screen or an old monitor? If a flat screen, is it big? I don't care one wit about the TV, I hardly ever watch it, but in this day and age, reasonably sized flat screen TVs are very cheap. Any place still equipped with cathodic tube TV tells you at once that they haven't done any maintenance/investment in a decade.
If the place "looks nice" and still has an old TV, you can pretty much bet your house on the fact that everything inside will be old and poorly maintained.
For higher end accommodations, look at the bathtub.
Knowing what furniture cost will give you a pretty good idea of the investment in the room decoration.
Photography techniques and lighting can make a dump look good, but they can't turn an old TV into a flat screen, and they have a hard time disguising the thickness of the bed linen.
- Amenities required. If you have a car, you need parking; you might want a gym, etc.
The goal of the first pass is to reduce your choices as fast as possible to a few good candidates based on objective criteria. Then you can dig into reviews. Diggin straight into reviews makes it an endless task.
Now that you have a short list of interesting properties, it's time to have a look at the reviews and ratings.
- Sanity check:
Quickly look at the rating score on a few different sites. Consider especially the rating score of booking websites where the user must have actually booked, paid and stayed at the place to be eligible for posting a review, like Agoda.
If there is a large discrepancy in scores, you know something is up.
Also, get a feel for the scoring system and how people tend to rate on the specific website. For instance, 6/10 on Agoda is rated "acceptable", but 6/10 really means "dreadful" because there is almost no place reviewed below 5.5/10.
Number of reviews:
Ignore score and reviews if there are less than 10 reviews unless the place is brand new. It's easy to override a poor review by writing 5-6 glowing fake reviews, but if the place has thousands of reviews, good luck with that.
Browse through the bad reviews and make note of recurring specifics. Discount generic comments. If reviews say that the place is not clean, that's generic, but if several reviews point out that the walls of the shower stall are filthy, chances are they are. Things like "scorched power outlets", "holes in the bed linen"...
If someone genuinely feels like the place is worth the lowest rating he is typically upset about it and will tend to exaggerate. He wants to get revenge and can be sarcastic but he will be specific about what went wrong whereas a competitor posting a bad will tend to stay vague about it.
Also note the date. Often you will see a bunch of reviews complaining about a temporary problem (no WIFI, power outages, etc.) If these complaints stop appearing in more recent reviews, the problem has probably been solved and the real score should be better.
Pay particularly attention to positive specifics in bad reviews. If several bad reviews admit something is good about the place, that bit's probably true.
- Browse through good reviews. Discard overly emphatic adjectives. Don't fully discard jargon, but look at it with suspicion (the reason why you don't want to dismiss it point blank is because frequent travelers tend to be fluent in hotel jargon). As for negative reviews, look for specifics. Pay particularly attention to good reviews admitting a problem that you already identified in the bad reviews. Some people have much lower standards/are less critical/nicer than other and will moderate their critics. "The bathroom was not very clean" in a good review will validate a "Bathroom were filthy" comment in the bad reviews.
Don't try to evaluate individual reviews on their own merits. Besides fake reviews, sometimes the reviewer is just an @ssh*le who treated the staff like slaves and expected a palace for the price of a bunk bed "because it's a cheap country". The review is not fake, but the reviewer is full of it. And similarly, you have guys who will leave positive reviews everywhere no matter how dreadful the place because their own standards are abysmally low. I have had genuine recommendations from Thai friends who marveled about places that can only be described as dumps.
Parsing the reviews and making note of specifics will usually give you a fairer picture of the place than an in-depth analysis of a handful of reviews.