Changing your formation to much causes way more trouble than it solves.

You should only change a tactic at end of season or if you're results have been extremly weak for a longer period.

Maybe having 2 tactics is an option but more than that results in more havoc than it solves.

I still prefer an attacking with creative football, works for me everywhere. (barcelona play > all) bringing Cisco Roma to Serie A in 3 seasons (hopefully, depends on 6 more games + play offs :P) with an attacking tactic and a very young team (21 avg). I've lose many points so far but it wins you games if you have the players.

Trying to tweak that gives trouble trust me

ok Andurilz is right about changing tactics.
Changing tactic too often is not good.

if you are weak team ,and play ahainst some big team i must recommend you 1-4-1-1-2-1


for this you need some sweper(some DC can train SW), than you need good AMR and AML.it is good that they have some good finishing ,because they will have chances.

other that i tried is 3-2-2-1-2.

your side back's must be good at wing back positions,and other positions are common.that AM should know how to score

note that these formations are not for long period,just for certain games.

about long period tactic,of course 4-4-2 is the greatest.would you play "line" or "diamond" it is your choice.of course 4-4-2 requires most common positions so can be played by almost any team.

and just a word about some tactics thing in FM08.
After period of a few months my team start to play bad,every formation lasts for some period and than i must find a new one.I read some posts on the internet about that and many people have this "problem".now maybe the game works like that,maybe other teams get used to your play,and learn your play so it becomes tougher.if it is true,well good job SI.But if this is not normal,than MAKE THE NEW PATCH.

and a word about those MANAGERS to tell that they need only one or two tactics to play this game.
i read many posts lately and i see posts like this(example):
i play great with just one tactic,in every match i go for win....bla bla bla. I PLAY WITH BARCELONA or MAN UTD, or CHELSEA , REAL........
the thing is ,they upload their magical tactics(they made with it great things), and then people download them for some weak team,well i does not work.THE BEST WAY TO MAKE A TACTIC IS TO LOOK FOR YOUR PLAYERS.
also when you play with strong team you do not have to change you tactics so often as you would with weak teams.
i started with Barnet in Coca-Cola League 2 and until Premier League i used 4-4-2 and against big teams from Premier 1-4-1-1-2-1.but in premier it is getting tough so i must change formation more often.

because of that i never post team and player instructions.
Formation can be shared,but NOT instructions.instructions depends on your players attributes.

than about players age,well i is good to have young players in 2nd,3rd,4th league,but in Premier you must have more experienced players.

Of course there are infinate ways of playing but a good starting point is 442 with attacking wingers. Have one central midfielder with a defensive mentality and the other set as an attacking playmaker. The defensive midfielder needs to have very good attributes for tackling, teamwork, stamina, workrate, passing, decisions, etc - basically very good mental attributes as well as tackling and passing. When playing a good team, get him to mark thier creative player in the centre of midfield. Your other midfielder (the playmaker) needs excellent passing, creativity, decisions, technique, first touch.
Have one striker as the target man and the other playing off of him. The target man needs to have very good stats for strength, heading, jumping, first touch, passing. The other striker is best to have great pace, acceleration, finishing, off the ball, composure, dribbling and techinque.
Set both centre backs mentality to defensive and forward runs never. Centre backs need excellent marking, tackling, jumping, heading, positioning, concentration and bravery. Don't use defenders who have very low concentration as they are prone to mistakes (Titus Bramble!!) and don't use defenders who are very slow as they will get skinned! Man marking works best across the back four. Set your full backs mentality to neutral. This way they won't bomb forward and leave you exposed at the back but still support the attacks when its down thier side.
When using attacking wingers it is essential that they are good players or the formation will not be effective as it relys on the wingers creating the majority of chances. Wingers need good crossing, dribbling, technique, passing, creativity, flair, pace and acceration. The quicker the better!
Getting the right blend of players is a good way of bringing success but you can only do that with money to spend so if you start with a team that has no money then you will have to base the tactics round the players you already have!!