Having travelled in the 'Shayanyan Shreni' (Sleeper Class) for a considerable distance on many trains, I have gathered some usefull tips which might be of use for others. (These are strictly my observations.. other might have views different than those of mine)
To start off: While booking your ticket, in the reservation form mention 'Mid-Coach-Inside-LB', in the preferences column of the form. (That is, only when you know that sufficient berths are available, and you can have the luxury of choice.) Also keep in mind, that if you do not mention any preference, you might even end up with berth no: 72(SUB), even if you happen to be one of the first guys booking your accomodation.
Why 'mid-coach'? (Berths 25 to 40 etc)?
The light from the corridors will not affect your night's sleep (if you are undertaking a night journey); the light from the coach ends invariablly illuminates the first and the last bays (1 to 8 and 65 to 72), much against our wishes.
There are chances that your luggage might be much more safer, if you are, in the middle of the coach. (Any person, near the door can walk off coolly with your belongings, at any roadside station, before you can blink an eye). Many of my friends lost their shoes, hand bags etc, just because they happened to be booked on one of the side berths towards the end of the coach, and were not careful enough. In any case, it is always better to secure your luggage with the help of a safety chain.
The smell from the toilets might not bother you that much, if you happen to be in the middle of the coach. Toilets do tend to stink badly within a few hours of commencement of journey, and this can be terrible.
An inside berth is much more comfortable, and is lengthier than a side berth. And for a tall person like me, side berths especially the side uppers are a strict no-no. And then you will not be quite disturbed, by the movement of people in the corridor, if you happen to be on an inside berth.
Lower berth: Well, you can catch up on some railfanning during the night. If its a full moon night, it would be even better. The sight of a WAP-4 or a WDM-2/WDP-4 zooming away, the twin headlights piercing the darkness of the night, those all clear green signals a few miles away, all these can be a treat to watch. Of course, invariably, you will get a request from a co-passenger to down the shutters. It is a safe practice to down the shutters before you hit the berth. If it's an overnight journey, and you have had a tiring day at work, then the inside upper berth would be more suitable, as you would get an unhindered night's sleep, not to be disturbed by the lights of the passing stations, the announcements etc.
It has been observed that during day time journeys, short distance passengers board SL coaches, and make themselves comfortable on our berths. I follow a simple procedure. I pull up the middle berth, and spread out my bedsheet and air pillow across the berth and stretch myself out lazily. This would deter many a short distance traveller from sitting on my berth. After all, why am I paying the SL class fare? (Let me hasten to say that this might not work under all circumstances.)
Beggars. They are ubiquitous. Ignore them. The blind couple types, who sing an apology-for-a-song, as they go about begging for alms... The women with crying babies-in-arms, who try to evoke your sympathy, with fervent 'please...' for milk, food for the little one. The floor-cleaner-urchin types... With a rag in hand, the small fellow will clean your compartment floor and then beg for alms. Some do it diligently, others just put up an act. The singing-balladeers: A small girl/boy with a couple of stones in hand, sing a popular movie song accompanied by the clackety clack of the stones. The card-droppers: A man or woman will quickly go through the coach handing you cards, that urge you to donate towards some orphanage, etc. and then come back, requesting for 'donations'. Don't be fooled! Eunuchs: Some 'request' money in a mild tone, others tend to get aggressive. Ignore them.
In almost all of the long distance pantry cars, you get dinner, lunch, etc., in casseroles. Some might be good, and others might be quite bad, depending on the base kitchen from where they have been obtained). You can either order the food from the PC, or best, get down at the major stations and check out the food stuffs available. Most of them are good; you get hot puris, or say any other food stuff, which is made minutes before the train pulls in to the platform. Omelettes, etc. - wash them down with a glass of fruit juice. (At Sholapur, you get some real good Paav Bhaji And Vada Paav, at Visakhapatnam, you get hot puris, dosas, etc.)
Toilets -- They stink most of the time making the journey a bit uncomfortable. What can be done?
Well at many of the big stations, you do have the sanitary staff clean the toilets with the mechanized toilet cleaner, but then again, as the train proceeds further, things are back to square one. Blame it, more often than not, on the passengers themselves, who do not flush the toilets properly.
All of you might not like it, but do what I do. Carry a bottle of Domex or scented phenyl with you. This might sound ridiculous, but believe me, it does save you from stinking toilets. Or just close your nose, and pretend that the smell never existed!
Also carry an old newspaper with you. Upper berths (or any berths or seats for that matter) can get quite dusty, and require a proper dusting. Safe drinking water is a must. You cannot trust even bottled mineral water nowadays, but then compared to the water available at stations, they seem a better bet. And a first-aid kit with medicines for stomach ache, headache, nausea, disinfectants, cotton, etc., might prove handy in unforeseen circumstances.
To conclude, travelling by sleeper class can be a pleasure or a pain. It's up to you how you take it. Thanks for reading this. As usual, comments are most welcome.