Generally speaking...

Generally speaking, how do you survive those early caster levels where you're still the squishiest person in the party and your spells aren't doing that much more damage than the melee classes so you can't burn down the orc who wants to remodel your shithole with a club?

try not being a faggot

try not leaving town without someone who can take a couple stabbings.

also don't walk down dark alleys at night. You might be accosted by a pack of cats.

Let the martials take a blade, it's what they're good for. If you're getting stabbed you've got a shit party.

>spells aren't doing that much more damage

Spells aren't for damage. Swords and knives are for damage. Any chucklefuck with a sharp stick can reduce an enemy's HP. You can twist reality to your will; if you're using your subtle and profound powers to do HP damage, you're fucking up.

Short answer: Don't cast Magic Missile, cast Sleep, Grease, or Web.

By not playing D&D.

Why would you need to survive? If your character dies, just reroll another one. Eventually you get to roll a high level wizard, it's just a matter of time.

What game? If dnd, specify which edition, because it varies a lot.

Befriend a tough party member so that he takes on most of the beating, and befriend a party member capable of healing so that he saves you from death when your tough friend inevitably fails to protect you.

And stay the fuck away from danger at all times.