How do I fix a misfiring engine on my Vauxhall Astra?

My Vauxhall Astra's engine is misfiring and I can't seem to figure out why. It started happening after I changed the spark plugs. What could be the cause and how can I fix it?

Julie, it's possible that the spark plugs were not installed correctly. Make sure they are tightened properly and the wires are securely attached.

Hi Julie, another possibility could be a faulty ignition coil. Have that checked and replaced if necessary.

Julie, check your fuel injectors as well. They may need to be cleaned or replaced.