The default settings that Team Fortress 2 comes in are pretty awful, with many problems such as a cramped field of view and a viewmodel held up to your eyeball.
So here?s a basic guide (nothing fancy like changing net settings or stuff like that) for people just starting the game to improve the interface and gameplay mechanics.
Changing field of view: This one is probably the most important go into options->video->advanced and move that ?field of view? slider over to 90. This allows you see more of your peripherals, and in my opinion the default setting of 75 gives a very cramped and claustrophobic playing experience.
Turn on Auto Reload::Unless you love playing spy (where the revolver reloading animation really blocks the screen) This handy setting will automatically reload weapons when you?re not firing, with absolutely no downside (except for the aforementioned spy revolver). Go into options->multiplayer->advanced and check ?automatically reload weapons when you?re not firing?.
Fast Weapon Switch: This makes it so you don?t have to scroll through the selection interface and left click everytime you want to change weapons, therefore saving some time. Found in options->keyboard->advanced
Damage Text: Highly recommended for newbies. It tells you exactly how much damage you do to the enemy, so you can find out that your shotgun is doing 3 damage at long range? go into options->multiplayer->advanced and check ?display damage done as text over your target? right now!
Medigun autoheal: Although veteran medics don?t use this, as they claim it makes it more difficult to switch between heal targets, I personally have never noticed any downsides. This option makes it so you don?t have to hold down mouse 1 the whole time to heal your target, which gets pretty annoying and tiring. Go into options->multiplayer->advanced and check off ?medigun continues healing without holding down fire button?.
?Viewmodel field of view?: the default viewmodel field of view has your character holding the weapon in first person basically at his cheek, this looks pretty silly and also blocks off a giant portion of your screen. Go into options->multiplayer->advanced options again and move the ?viewmodel field of view? slider to a higher number (whatever your personal preference).
Hitsounds: This makes a little ding whenever you hit your enemy, not extremely necessary unless you love demoman or soldier, as the sound is pretty annoying especially as Pyro or Heavy. However, it does give you an advantage in combat with no downsides (despite the aforementioned annoying-ness). Go into multiplayer->advanced and check off ?play a hitsound everytime you injure an enemy?.
Medic Auto-call: This handy little setting will display a small red cross over any teammates whose hp is below a certain percentage specified by you. Found in multiplayer->advanced.