Like software development, fitness has many methods and plenty of adherents that will swear by each one. Unlike software, however, human physiology doesn't change very quickly. Generally, simpler is better.

In general, you should mix cardio work with lifting heavy things. The ratio will depend on your goals, as will the kinds of lifting you do. All things being equal, exercises that involve more muscle groups and larger ranges of motion will burn more calories than isolation lifting (which is what most machines are set up to do). If you have weak joints or other physical constraints, machines can be a good place to start, as they will provide you some degree of support and help with your form.

Part of the reason you hear about so many methods is that so many of them work. Most are greatly oversold, and in the long run you'll find out what works best for you and ignore the cookbook-style exercise plans, but anything that motivates you to create a fitness plan and stick to it in a disciplined fashion is a good place to start. In fitness, consistency creates more progress than efficiency, and premature optimization is still the root of all evils.