Premier Manager for the Mega Drive can be an exceedingly difficult game, so you'll need all the help you can get as you attempt to bring your squad from Division Three also-rans to Premier League contenders. Here's a few quick hints which will also work on the 97 version, and possibly the Windows/DOS version.
Some general notes
The instruction manual talks about shooting distance quite a bit, explaining that the better players will be able to score from further away. However, you have to take into account the relative skill level of the opposition, which, apart from the cup ties, is likely to be round about the same as you. Unless you're up against an absolute donkey of a goalkeeper you'll be pretty lucky to hit the net from anywhere outside the penalty area. I don't recommend long range shooting as a general tactic - I usually get more success from medium.
One thing that's always annoyed me slightly about the Premier Manager series is the skill ratings indication system, where a level out of 100 and a written form like 'V Good *****' (see screengrab below) are interchangeable. This is most annoying when employing staff - their percentage stat isn't available, which can result in you having to consult the manual every ten minutes to try and find out whether 'outstanding' is better than 'exceptional'. Here's a better way of ascertaining staff skill: look at their wages. Generally, at the very toppermost level, just over £1,800 is the best you can get.
This will sound incredibly obvious, but... the best way to keep players' morale up is to win: if you're steamrollering everything in your path, then even subs and reserve players will benefit. It does make a world of difference to your performance, especially in a 50:50 match situation.
Once you're in the Premier League, you'll get access to the better youth team coaches. This will allow you to bring in higher quality players from the youth academy - think 18 year olds with skill ratings of 75+ when they are promoted to senior level. With a good team of coaches (check the Job Centre each month when the sponsorship deals come up for renewal), these can be trained up to 99 within a few years, and are slightly more financially beneficial than bringing in new blood via the transfer market.
For the reason outlined above, I don't recommend using the transfer market unless you really need to. Players are pretty much always overpriced, and that's before you take into account their wages, which can cost you a bomb. Invest in youth - it may take a bit longer but will be better in the long term. Of course, if time is of the essence, then you may have no choice but to buy. This might require selling two of your existing players, which is always a bit of a risk, but one you may have to take.
Note: Look out for the youth players named after members of the programming team such as Atkinson, Lister and Casson. They aren't necessarily any better than any of the others, but it is curious that programmers succumb to vanity: see International Cricket Captain etc.
Stadium and sponsorship
The higher a stand's capacity, the more sponsorship offers you are likely to get for it. Building covering will also allow you to have more hoardings on that stand. If you feel so inclined, take your time when selecting sponsors to ensure you're filling all the space available on the hoardings: in particular, look for Pay Per Week deals.