Electrum backup

[yarnyy]

Should I backup the wallet file everytime I make a new transaction?

[TheQuin]

There is no need to do that. You just need to make sure you have safely stored the seed phrase so you can use it to recover.

[bob123]

This was necessary in times where wallets pregenerated a fix amount of addresses. At this time you had to back your wallet.dat up every time a bunch of new addresses have been generated.
Most of the wallets now (including electrum) are using Hierarchical Deterministic (HD) wallets (https://en.bitcoin.it/wiki/Deterministic_wallet).
This means your 12 word seed (which you were prompted to write down at the initialisation of your wallet) is used to create private-/public- keypairs.
You can think of it as a mathematical equation: newAddress = mathFunctionOn(seed) + counter.
So backing up your 12 word seed phrase once is enough to be able to restore your coins into any BIP39 compatible wallet.