Want to save money on flights, I wanted to travel from Manchester to Athens and the choices are expensive. However, I booked with google flights, Lufthansa via Munich, got my seats free, baggage free(23KGS) £411 for two, Easy jet £769 and BA £1390 for September so no contest.
I told a friend of mine who was trying to get cheap seats manchester to New York. He had been quoted £1400 for two, but when he did Lufthansa, he got two tickets for £786. By booking with Lufthansa, they are part of the Star Alliance Goup like BA is part of IAG. Lufthansa searchrd their partners and offered him Manchester New York (EWR) direct with Delta Airlines.
Now thats quite a saving folks and better than your Ryanair type of airlines.
Just to clarify a couple of points:
Firstly, Star Alliance & IAG are not similar. IAG is the group which owns BA & several other airlines; Star Alliance is an alliance of a number of airlines, mostly under different ownership, which work together to offer codeshares on each others' flights. BA's equivalent is One World.
Secondly, Delta isn't a Star Alliance member (it's a Sky Team member) & doesn't fly MAN-EWR direct; I think you mean United!
Airline pricing is a very complicated business, but unless booking as a codeshare is significantly cheaper it's better to book with the operating airline - things such as seat selection can be difficult (edit: according to complaints on travel fora) if you book through a codeshare partner. As for cost, you need to balance the convenience & shorter overall travelling time of a direct flight against the lower cost of a one or more stop routing.
Edit: don't search for "cheap flights" - that can take you to some very dodgy so-called "Online Travel Agents" who don't have live pricing. Search onGoogle Flights & book direct with the airline.