What are some extra (mustahab) zikrs to use in different parts of an obligatory prayer?

I've been wondering how one can lengthen their prayer -in order to remain more in praying condition- by using extra zikrs in ruku', sijdah, tashahhud, salaam and so on? I've heard that any prayer in praise of Allah is permissible in sijdah and ruku. I'd be glad to know if this is true, and if so, what are some more common/accepted suggestions. What about tashahhud and salaam, please?