Depending on what you read or who you speak to, this varies from nothing to as long as you feel you need to!
Warm Ups are important prior to your training session as it pumps nutrient-rich, oxygenated blood to your muscles as it speeds up your heart rate and breathing. With my clients a good warm-up utilises all major muscle groups and lasts for between 10-20 minutes. For best results, start slowly and increase the intensity. To make warms ups more interesting, try using more than one piece of equipment and keep the transition time as short as possible as so to maintain your heart rate.
Good examples of equipment you can use are rowing machine, cross trainer, ski erg or watt bike as these use the majority of major muscles in your body. Treadmills are exercise bikes are also good but they mainly work the lower body.
Another element of your warm up should be the consideration of stretching. Again this is a topic that has mixed opinion amongst coaches, but I follow the approach that if your workout is specific or intense stretch or introduce exercise that mobilise and stretch the muscles involved all together.
Finally, you may want to consider the use of a massage gun to help get rid of any niggles or tight spots prior to training as part of your normal workout schedule. I have a Theragun on hand if required but pressure point balls, tennis balls and bands work just as good.