Tactics
Wargamers want to know how armies fought: ranges, weapons, deployments etc. This section is where I have placed all such material that I have found.
Most of it isn't new to the site, but some of it was tucked away in not very obvious places.
Suggestions of other sources, especially those of participants, is most welcome.
Instructions or Guidelines
Eikhe's book on RCW tactics for the Red Army in Siberia. 
This was written by a man who commanded a Red Army division, and briefly an army, fighting Kolchak's forces. He discusses almost every aspect of the front-line combat, most illustrated with detailed examples. Not all of it applies to the other theatres, but a lot of it does. There's also quite a lot of Orders of Battle. Please contact me if you want a copy of the Russian.
General Timanovskiy's instructions for the AFSR's 7th Infantry Division. 
This was written in mid-1919 and describes how the White armies might deploy platoons, companies and battalions. My thanks to Cuprum for supplying it. The original Russian is here.
Broniewski's paper on Polish infantry tactics
Written just after the war, it discusses what was generally done during the 1920 war, before suggesting improvements.
Arczewski's conclusions on fighting cavalry
This is the conclusion section to the book Ostrog - Dubno - Brody which describes the campaign of the Polish 18th Infantry Division fighting the Soviet First Horse Army, and describes how infantry should fight cavalry. The full book is here.
Observers
This starts with his time with the Poles, but concludes with comments about tactics, mostly about Polish artillery.
This includes discusson of Polish and Soviet cavalry tactics.
Captain Moslard of the French Army
Discusses the Polish 1st Cavalry Division, with reasonable detail on technical matters. A second part deals with some of the actions he witnessed.
General Shinkarenko of the AFSR cavalry
This is the record of a lecture given on the use of cavalry in the AFSR by a fairly senior commander.
Mamontov of the AFSR horse artillery
This is a small section of Mamontov's memoirs where he discusses some of the specifics of the horse artillery. The full book is here.
Secondary Sources
Red Army in the Kurgan-Petropavlovsk Offensive
Some discussion of techniques used by the Red Army during this operation (Siberia 1919).
Red Army tactics on PygmyWars
Each troop type has some discussion of what I understand the most common tactics were for the Red Army.
A Russian account of the nature of the fighting in the very early part of the war, before properly formed armies even existed.