There is a ton of the warm up exercises and variations of each one, just like the techniques and the entrances. Changing a speed of the same move can make you feel different. No matter where you do aikido – a class is going to start from a warm up most of the times. Warm up exercises are usually the simple ones to do. They are about stretching, breathing, unlocking your joints and preparing your body for a harder work. You are trying to get a detailed feeling of these little parts of your body, preparing your mind also and concentrating on the present moment. These simple moves will tell you how hard are you able to go this time. You must try to remember this every time you start a warm up. It’s not only a tradition.
There’s a kind of a standart group of the warm up exercises in aikido. A bank of the moves for your preparation that fit in a best way. A good example of the way standart aikido warm up looks like by Morito Suganuma.
A count is big enough and growing when some of the Senseis are making the innovations. Like Tamura Sensei who integrated Jikyo Jutsu moves in his aikido lessons. Jikyo Jutsu is a Japanese method of health exercises. It’s a standalone system in a first place and was not desidned for aikido warm ups but it fits well. It’s very popular among japanese people. Pictures of the original Jikyo Jutsu guide are included in a video.
Basic aikido warm up with breathing kokyo-ho elements from Valery Skryliov. He is a President of the Aikido Federation in Saint Petersburg and Leningrad district. Valery is doing martial arts from 1970 and has experience in freestyle wrestling, sambo, judo, karate shotokan. Today he holds 6th Dan Aikido Aikikai, 6th Dan Daito-ryu Aiki-jujutsu, 5th Dan Jojutsu, 4th Dan Kenjutsu. He’s an official representative of Yoshimitsu Yamada Sensei in Russia.
You can do warm ups with the weapons. An example with Jo by Chiba Sensei who dedicated much of himself to a work with weapons.
Ukemi exercises of course. You are going to to do ukemi in later stages of your practice anyway. So better start it slowly by yourself and try to make a job on details you know your not good at to improve before you will be forced to make the same with your tori (the one who performs a technique). Meeting the Mat video from Donovan Waites post contains more info and explanations.
Options are countless. Warm up is good way to start it simple and move on to more complicated moves bit by bit. Be sure to warm up before the practice, this will save you and your practitioners from traumas and will make your mind confident about thing you’re about to do.