Game Scheme:

Ok everybody, repeat after me...
"Dogfighting is useless... dogfighting is useless....dogfighting is useless"
As any good player knows, dogfighting ability means squat!  All you need to be able to do is suicide.. if you can do that, then you can be a good player.  Dogfighting skill used to be something that everyone thought was mondo, until that great guro of netrek, terence "God" chang taught us CMU *veterns* about ogging.  To be a good, respected player (IMHO) this is what you need to know:
  1)  How to observe the "flow" of the game on the galactic map without being a free kill on the tactical.  This includes the following:
    a)  Spotting when people pick up armies (either from the net-blink that occurs when they pick up, or by observing how many armies are on a planet prior to and after the suspected carrier leaves.
    b)  Learning to guess which planet a carrier will go for and proceeding post-haste to that planet
    c) Learning to observe group enemy movements and determining if they are ogg waves/escort waves or just coincidence.
  2)  Learning to type and respond to messages without needing to fly away from the front. 
  3)  Learning that speed kills, and always go max warp when not fighting someone.
  4)  Learning to think ahead of time, and always know what you are going to do when you come back in at your home planet.  This can include the following:
    a)  Continue to ogg the person you missed
    b)  Kill a bomber that you noticed going to a core world
    c)  Grab a base to store armies
    d)  Scout bomb if you noticed no-one is doing it
    e)  Ogg another suspected carrier
    (Note: There are not in any particular order)
  5)  Learn to spot people with kills and know who carries with 1 kill, and who likes to wait until they have 2.  This also includes the following of their movements on the galactic.

These are 5 major attributes that I think seperate a "clued" person from a newbie.  A newbie concentrates on the Tactical display, and hense fails to observe the entire "play" being performed about him.  A "vetern" (to use the term loosely) spends more time watching the game evolve on the galactic map, and only concentrates on the tactical when he/she has arrived at the location that they desired.  As the samurai maxim says, "A person who has mastered an art, reveals it in his every action". [Kevin Michael Bernatz]

     I think the real issue is that netrek is played on two different levels. There is the upper level, where ships are fighting eachother; and there is the underlying level, the armies being nuked and planets being taken. I think the more clue you have, the more you worry about the underlying level. The less clue you have, the more you worry about fighting enemy ships.
     There's very little reason to hang around the front and dogfight people when you could be off bombing or ogging. If you're trying to "win the game" you need to destroy all enemy armies. So pick a role: bomb, ogg, or beam. The only place that dogfighting fits in here is picking up kills to be able to beam.
     It's true that dogfighting skills will keep you alive in many situations, so it is usefull to learn good dogfighting. The best time for that is on an empty server, before tmode starts up.  That's the only time I dogfight. Once that "t" flag is in your tstat window, you should be working towards winning the game. If you're still dogfighting, you're not being useful to your team.

The game is over when a race has conquered 3 systems, that is, they own 10 out of 10 planets in 3 quadrants. Note that the enemy can own all of its planets and still lose! If one player distracts the robot (a nontrivial task under Tmode conditions), his teammates can snarf the robot's planets.
This is a good strategy to use when you already own 2 systems and the enemy is stubbornly clinging to its last few planets. That neutral quadrant probably already has several planets that don't belong to the robot. [Terence M. Chang]

What prevents planets from accumulating 100+ armies? Plagues. Each planet has one every five minutes or so. If there were N armies on the planet and there is a plague, the number is reduced to random number between 1 and N.
If you are trying to snarf all of an undefended team's planets, this is how: you should keep an eye on the army count of all of the planets. As you wait, some counts will drop below 10. Beam down on these guys.
Morality note: Mucking about with neutral (robot-guarded) planets is way uncool unless you are trying to conquer the galaxy. The more spread out the "planet contention zone" is, the more degenerate the game becomes. [Terence M. Chang]

[I wrote this a long time ago. i still believe that the DD is the best "all-purpose" ship, but i never play one myself. the reason is that though it is very flexible, it is best at none of the *fundamental* tasks at hand (bombing, ogging, taking). today, i play a scout almost exclusively.]

ships:

I usually play a DD because I think they are the best all-purpose ship. On a moment's notice, you can do anything: ogg, deep bomb, take planets, or defend planets. I think scouts are certainly superior for deep bombing, AS for initial bombing and defended planets, CA for getting kills (or playing in the 3rd race's space), and BB for point defense. I find their only big disadvantage is lack of fuel. You also have to be more careful about overheating your engines than you would in any other ship, but you should almost always be able to avoid this.
Sometimes I'll play a SC even though I'm not bombing because the enemy is doing a good job of bombing, and I want to get to the armies before they do. I'll play a BB when I'm frustrated, and feel like frying those enemy foolish enough to stray into my space.

I'm going to post my usual "state machine" as I understand it. I invite criticism and comments.

opening moves (still planets with 25+ armies)
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1) in AS, bomb bomb bomb. goto 1.
interrupts: if I am near an enemy bomber, kill it, but don't spend more than 5 or so seconds.

if there are only 1 or 2 planets with 25+ armies, and I have teammates who appear to be taking care of them, and I have 2 kills, then commence mid-game play.

mid game (everything between opening and end-game)
==================================================
1) in a DD, ogg enemies with 2 (sometimes even 1) or more kills. repeat until there are none, or my team has lots of spare armies. goto 2.

2) still in DD, get a kill. if there are any "weak" (3 or less armies) enemy planets, get armies and try to take it. If not, get another kill, then start taking planets. keep taking planets until i die. goto 1.

interrupts: if i appear at the home world in either SC or DD, and there is a bomber, go kill it.

if there is a front-line agri that needs defense, do that until it pops.

if someone needs help taking a planet, do that, unless i'm trying to take planets myself.

note: if the enemy has more planets than we do, spend more time ogging.

their end game (enemy has only core planets or less)
====================================================
1) in an AS, get a kill or 2. goto 2.

2) get armies, get help, bribe tc2i (a doughnut usu works), take a planet. goto 1.

interrupts: if teammate requests escort, do that unless also carrying or about to carry. then suggest coordination.

if they have a planet that can be bombed, do that.

if any enemy carries, ogg (use DD or CA).

our end game (we have only core planets or less)
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(3 or fewer planets) in a BB, guard a planet. leave armies on the planet.

(4 or 5 planets) ogg everything.

overriding principle:

your life has very little value. spend it freely. [Scott Draves]