Different people have different ideas on what constitutes the perfect practise session. Some are happy to arrive at the dojo, have a quick stretch, put their men on and enjoy an hour’s jigeiko. Others may prefer to concentrate on kihon drills for the whole session.
In my view there is no right answer. The way you structure your keiko depends on how much time you have to fill and the level and physical condition of those taking part. If you are lucky enough to have a number of kodansha in the dojo, then jigeiko can be a great learning experience. To be more precise what you are getting is hikitate-geiko, where sensei is taking a view of your strengths and weaknesses and stretching you to do a bit better. If there is one instructor teaching a class of students then a structured session built on demonstration and repetition is likely to be the best way forward.
The length of your training session also dictates what you do. My ideal kendo week would consist of five or six 45 minute to one hour practices, each conducted at maximum intensity. When you have two or 3 hours to fill, you need to bring in more variety and exercises that offer a change of pace. For example, start with kata or boken ni yoru kihon keikoho, move on to kihon drills, keeping them short and changing partners frequently and finally move to jigeiko.
With kihon drills it’s best to keep to a theme. It might simply be improving ki-ken-tai-itchi, or could be something more ambitious like incorporating seme into the attack. You can work on shikake-waza one day and oji-waza on another, or you could practise men attacks and the oji-waza to use against them as part of the same session. In drills like this it is important for both motodachi and kakarite to approach each technique with total commitment and not anticipate the others movement, otherwise you are in danger of producing the counter attack before the attack.
One other word of warning, don’t try to do too much. I have seen sessions which have included almost every technique in kendo. In this case it is difficult to remember what you have covered, let alone get any benefit from it.
However you approach each training session remember that the purpose is to improve your kendo, and to enjoy your time in the dojo.