The machine should feel smooth when you are using it. Throughout the full range of motion there should be no interruption in the movement — no jerking or hesitation. Testing the least expensive equipment and comparing it to the most expensive equipment will clearly show what smoothness is.
The machine should fit your body. You will need to use the correct form while performing the exercises when testing a machine. Have the salesperson help you so that you try to perform as many of the machine's movements and exercises as you can. You should feel the exercise in the right place — meaning that if it is supposed to work your chest, you should feel it there, not in your joints or lower back. You may just need to adjust the seat, but the machine just might not fit your body.
The equipment must fit into your home. Before you purchase measure the dimensions of the space. You will want to note the length, width and height of the space. Compare this to the home fitness equipment's measurements taking into account the range of motion of the machine. Today's equipment is often very space efficient; you may be pleasantly surprised.
Choosing between a treadmill, a stair climber, a rowing machine, a home gym or an exercise bike. Each piece of home fitness equipment has much to offer. Which is best is dependent upon your fitness goals and your preferences.