A few remarks will help you remember the many command key sequences. All paragraph mode commands (\textbf, \footnote, etc.) begin with <CTL OPT> or <SHF CTL OPT>, whereas all math mode commands begin with <CTL CMD> or <CTL OPT CMD>. All environments are bound to some modified function key. Sometimes the <SHF> key reverses the orientation of an existing key (as in the case of Next Tab Stop and Prev Tab Stop described in section 2.1.1) or acts as a selection key (see, for example, Next Environment and Next Environment Select in section 2.1.1). Knowing these simple facts helps tremendously.
See section 1.2 for pointers to useful command key summaries.