*picks a few cobwebs off the Tips/tricks section*
Right, lets start with the basics:
Check ALL corners: Regardless of whether they are usually 'occupied/camped', this could be the difference between life and specing.
Learn where people camp: How many times have you been killed and thought to yourself "I bloody knew someone would be there.... Camping sod!". Do yourself a favour, remember these spots and if in doubt, throw a flash.
Flash FTW!!!: A well timed and placed flash can easily get you a kill or more;
1. If you are approaching a doorway, drop the flash just round the corner of it, bounce it off the doorframe if possible, most people who likely to have tents set up behind doorways will be close enough to get a full flash
2. If you are being chased around a corner, turn and face the corner, drop the flash just after you turn it. The enemy shouldn't see it get thrown and will run into it... leaving you a good few seconds to avoid there hopeless spray and pick them off with ease.
3. NEVER aim the flash directly at an enemy, trying to hit them... yeah a flash kill would be cool, but if you miss, they wont be flashed and you'll have turned around to avoid the flash... you'd die

.
4. Simplest point, Never leave spawn without one (two if you have money to spare*
OMFG I'M FLASHED!!!1one!: if you are surrended by teammates... dont fire... many a needless ragdoll have been wasted due to nubs spraying when flashed. A few options;
1. If you know the layout of the map well, find somewhere to camp it out.
2. If you know where the flash came from, adjust your aim and fire away... the second the flash begins to wear off you will be able to see something moving (
WARNING: You will be called a haxor if it works 
)
3. If you don't know where it came from and can't find somewhere to hide... jump and strafe like a total noob, the more disorganised the movement the better, if you don't know what you're doing it's hard for an enemy to predict it. A moving target is much harder to hit.
That sounds familiar: Hear the click of a flash or a HE grenade, panicking like crazy? GOOD! You should all recognise the different noises the grenades make when hitting a wall or floor (if not, create a server and get tossing)
IF... It's a flash grenade, if you know where its coming from you could save yourself alot of hassle, I only use 2.1 sound but it gives me an indication of what direction i should turn. Make sure you get close to a wall, this should give you a bit extra protection against it. Chances are in open combat you will see where the flash is coming from, just just turn your back and hope it doesnt go to far. If you have seen the flash go high, turn and crouch, if it's low, turn and jump. Every little bit helps.
IF... Its a HE grenade,these are thrown faster than you can run so don't run with it, run past it if possible, if not strafe. HE 'nades are more visible when thrown than a flash, or smoke, so if you hear one have a quick scan around... then leg it. Hiding behind a box, or getting round a corner can take alot of the effect away, sometimes stopping you getting hurt at all. In the past I've been hit in the face with a 'nade, ducked behind a box and taken no damage.
Fire in the hole: PRACTICE THROWING THESE THINGS BEFORE TKING!!!!
WARNING: Pisses people offGood maps to practice being a good tosser are;
de_subway_2: The vents at the top of each spawn are a good target for practicing on. de_clubdome_b2: Again, The vent at CT spawn is a good target from the floor near the barrels. cs_Italy: close combat, lots of corners, good practice for flashbangs, make sure you have some bots on your create server.Grenades are the one weapon I would call myself a pro with (type ?foxx into SBG and you get 'nade master')

So for this section, I honestly do know what i'm talking about.
ALWAYS make sure you have enough time to throw a grenade before being shot to hell. It takes roughly the same time for a HE nade to explode as it does to be able to shoot again, bear this in mind for close combat nades.
NEVER aim low and run backwards when throwing... trust me (insert suicide here).
NEVER aim at an enemy in close combat with a nade, aim for the feet, that way it won't come back at you (suicide 2)
ALWAYS check your radar before throwing round a corner/doorway/etc
(TK-tastic)
For:
Long Distances: run with the grenade when releasing, travels a good extra 50% further. Don't aim too high or it'll go boom before it reaches anything.
Mid Distance: This is the easiest distance to kill people at, if the person is running, predict where they'll be in 3 seconds, then release. If they're stationary the job is alot easier... press and release.
Close Combat: Throw the grenade behind your target, or if theyre far enough away to get minimal damage, aim at their feet.
IF... you run into a full room armed with a grenade... you won't have time to switch back, take one for the team

Throw it where the most enemies are, remember it's a team game, 60-80 damamge to 2 or more enemies is better than 100 to one.
Remember kiddies... windows will shorten the distance of a grenade by a considerable amount, so shoot 'em first.
Practice throwing them against door frames, window frames, off objects like cars on some maps (campers in the van on cs_twilight... get it in the van and they're doomed

)
Spray and Pwn!: Hated by players everywhere, the best close combat weapon of all, trusty p90!! *applauds*
Back in the day, when i first got CS

the M4 was faster and a bit more vicious, rather than the mini sniper rifle, sans sight, that it's become now.
The p90 has taken over from the old M4, with very little recoil other than side to side, its the perfect close range weapon... and easy as hell to get a headshot with. (just make sure you have a strong pistol for distances)
Run AT people at close range and make sure your aiming high, head and chest is much better than nuts and kneecaps.
MMMMMMMM4: If this gun were a woman....

I have a fair few kills with my trust M4... but only 3 of them have come from an unsilenced M4. Moral of the story is;
Power is nothing, without accuracy. maybe an unsilenced M4 can kill in one shot to the chest at mid range, but a silent one can kill in one shot to the head still.
GOLDEN TIP OF THE DAY!!!When fighting close or mid range with a silenced M4, aim for the neck... recoil will do the rest. for close range with an unsilenced M4 aim for the chest, aim for the stomach at mid range combat.
Fancy pissing off a sniper? move in a disorganised manner, always aiming towards the sniper, but dont shoot, wait for the BOOM > crouch > aim for the head (been 60 and 120 feet the cross hair when crouched should be accurate enough to hit the head atleast once if you pop out a quick 3 shots) BOOM M4 HEADSHOT and one pissed off sniper.
I'll post a few tips on camping and headshots later
