Sizing is not critical, but roughly 6 to 12 inches taller then your height is a good fit. Too tall is better then too short as you can choke up on a long one.
Do not leave them standing in wet snow for days at a time as they are wood and will soak up moisture. If the Tiak starts to look dried out (especially on the bottom end) you can oil it. We use a linseed oil mixed (50/50) with paint thinner or kerosene (this allows for better penetration into the wood).
Tiaks are made of Lodgepole pine, selected from dense stands that grow in higher rocky terrain. This makes them very slow growing and strong, with a typical 1 ½ inch diameter selected tree being 50-60 years old.
Tiak means, literally, stick in the Kazakh and Tuwa languages found in the Altai.