Ok> OLD SCHOOL SF2 CRASH COURSE
#1
Do not jump. There is no blocking in the air, and EVERY CHARACTER has anti-air moves, it's just a question of whether they know how to use them or not. If your opponent is a noob, and won't stop throwing fireballs as Ryu, sure, jump and punish him, but any SF player worth their salt knows that the first and most fundamental strategy for advanced play is to PUNISH THE JUMPER. Don't be a dump jumper.
#2
Learn the strengths of your character. SF2 is old enough that each character is strongly defined by one, two, at most three playing styles, with certain MEAT and POTATOES moves and others obviously just weak and unusable. For example, Ryu, his sweeps and fireball/dragon punch make up his main arsenal. Fireball the enemy when it's safe and play the ground game by using crouch forward into fireball to wear away at the enemy's life. Crouch roundhouse if they do a move close to you and miss completely, and use short (both crouching and standing) to counter enemies who have better reach. Bait the enemy into jumping by getting off safe fireballs and then faking them into jumping when you actually haven't done one, punish with dragon punch or crouching fierce/standing roundhouse. Ryu/Ken's crouching fierce is a phenomenal anti-air move against 80% of the other characters, but do not use it against Chun-Li/Blanka/Vega/MBison, these guys have very high priority air moves that require a dragon punch counter. Guile is infamous for being the most terrible jumper in the game, he travels far and slow in the air and is EASILY punished in the air.
#3
Counter tick throws by pulling away (joystick or pad) from the opponent and hitting the throw button. Tick throws can be a cheap way noobs use to get easy wins. The basics of the technique is just to get in as close as possible, do a jab (usually crouching) or short, send the other player into their blocking animation, and then push forward and fierce/roundhouse for a throw. This works because the light jab/short doesn't push the blocking player far enough out of throw range, and because the animation of the defending player goes from blocking immediately into being thrown, it looks almost automatic. But what most noobs don't know is that the defender can input throw and counter even in blocking animation. Just pull back away from the attacker and tap on your thrown button when you are in blocking animation, if you are pulling back and hitting throw, you will ALWAYS have higher priority.
#4
If you get cornered, don't stay there. Being in the corner essentially means you have only 2 directions to go, forward, or jump forward. Since jumping straight up gets you nowhere, being in the corner makes it THAT MUCH EASIER for the opponent to anticipate a mistake/opening and attack you.
#5
Don't play as E Honda, that fat bastard just doesn't cut it in old school SF2.