The BCP car park is nearby, and has a frequent shuttlebus service to all the terminals.
Theres also a train station inside the airport, connected by bridge (with moving walkways) to T1 and T2: - there's loads of trains throughout the day (and well into the evening)
Train fares are reasonable, - and if you're struggling to find cheap advance fares online buy an advance to manchester piccadilly and a separate, standard ticket from there to the airport. This is usually a lot cheaper than buying a standard ticket for the whole journey.