Before you set out on your BAM trip the main thing you need to consider is that this trip is not for those who like luxury and expect everything to be ideal. The tourist infrastructure along BAM is not perfect. Firstly the trains themselves tend to be older than usual and there are no premium compartments on the route. Your ticket though should tell you whether your train has a bio-toilet (which remains open during stops), air conditioning and food options. Secondly the cities and villages along BAM themselves do not have well-developed tourist infrastructure. Hotels tend to be simple, and sometimes expensive if there is no alternative, and the same can be said about restaurants and cafes. However this is part of the point of a BAM trip, it's a journey somewhat away from civilisation!
The schedule of the trains is not always too convenient. Sometimes you will have to spend all day on the train and then get off at your destination in the evening. However the views out of the window do make up for this to some extent.
Finally the spectacular nature you will see is really wild! In summer months, you will need to take all the proper precautions against mosquitoes, gadflies and ticks - repellent and special clothing are essential. The mosquitos are vicious and very annoying, but disease free. Ticks here however can transmit Lyme’s disease and tick-borne encephalitis. There are other bugs too - such as longhorn beetles that fly and can get stuck in hair. They can bite but are otherwise harmless.
There are also bears and on some nature walks you will certainly see signs of them! Any normal bear should move away upon hearing humans approaching, so it is best to speak loudly or wear a bell on your walks. If you are unlucky enough to encounter a wild bear, the best advice is to back up slowly - never run, it will catch you; playing dead might work if you are actually being attacked. But let’s face it, your chances are slim in case of a bear attack! Therefore it is best to stick with guides who know the local area and not to wander off into forests alone.
Finally you need to appreciate the remoteness of some points of the trip. If you are unfortunate and fall ill on your trip or injure yourself the nearest decent hospital might be very far away. Good medical travel insurance is of course a must. In addition, in places you will be out of mobile coverage and there is only internet coverage in cities and larger settlements on the route. Also, should you need to suddenly return home, it might take several days to get to the nearest airport.