Identifying hits to the iRule.

You can use log statements in the iRule, which will send output to /var/log/ltm

log local0.debug "text"

A common method is to use a debug variable, so you can turn it on and off easily

At the beginging of the rule

when RULE_INIT {
    set static::debug 1
}

and then in your code blocks

if { $static::debug >= 1 } { log local0.debug "Text" }

change the static::debug to 0 in RULE_INIT to shut off logging, use values greater than 1 for more verbose levels and so on.