Against the AI it doesn't make much difference, but against a human player this works wonders. If you are the one with the Plasma torpedoes, use the Pseudo Plasma torpedoes to fool your opponent. Now, attack that ship! Plasma torpedoes replenish slowly, which allows you to attack multiple times before the enemy is able to launch another one at you. The torpedo will either inflict very low damage, or won't hit at all. The plasma torpedoes dissipate over time and lower the damage you will take - so, if your enemy launches a Plasma torpedo at your ship, run to the opposite way. If the enemy has Plasma weapons, always keep high speed (20+). By knowing the other's ship specification, you'll be able to easily develop a strategy for the upcoming battle. If they are more than one, launch it at your strongest enemy. When you start a fight, always launch a scan probe at your enemy. It will make you game more interesting and more challenging.
Always accept the places in your chosen race's Special Corps. I don't think you'll survive to purchase a battleship immediately. Or if you can - something even bigger, like a Dreadnought. THE MORAL FROM THIS STORY: you should reconsider having a tough time at first and jump from a Frigate to a Heavy Cruiser in one shot. In addition, when you gain ranks, the ships in the shipyard will grow cheaper. You will notice, that the selling of a purchased ship immediately lowers it's price. Later, you sell the NCD+ for a Heavy Drone Cruiser (F-CAD) and so on.
But as soon as you see that you can get a Light Cruiser, you sell your current F-DWD and buy a New Drone Cruiser with Plus refit (F-NCD+). The ship is great, you win missions easily. So you sell your Frigate and buy a War Drone Destroyer (F-DWD). You play two missions, eventually successful, then check the prices in the shipyard and discover that you can buy a War Destroyer if you trade in your ship and add the current prestige. For example - you play the Federation campaign. Lots of players buy ship after ship, once they see it's a bit stronger than their current one.
In the manual you'll find the damage dealt by all weapons in the game, which will help you develop an adequate strategy. At least, play the tutorials if you don't want to waste time reading. Don't play a game if you are not familiar with the race you have chosen. Lots of things are explained there and I can assure you, It'll be worth the time you spend reading.
Read the manual included with your copy of the game. For example: F-CAD+ means Federation Heavy Drone Cruiser with Plus refit. If you don't have the SFC manual, I'll give a brief list of all designations in the end of this FAQ.
NOTE: I will use the ship's designation all the time. Know this when you play Starfleet Command Volume I. The victory, achieved with lots of difficulties on the way is the sweetest of them all. Save the game before every mission and try different approach. You'll need some time to do so, so don't flame in vain when your ship is destroyed. I would like to point that it's not easy to learn the ropes of this game. I will put all missions one after another with their original names so that you can easily find where you are and search for tips or help. It covers some tactics and a walkthrough for all of the campaigns in the game.
This FAQ is based on my personal experience in Star Trek: Starfleet Command Volume I PC game.