I am not aware of any "rule" that makes it possible to recognize a specific verb as being ditransitive or not, so my initial reaction was "consult a dictionary", however some online dictionaries seem to be lacking in this regard. I am quite surprised that neither dictionary.com nor merriam-webster make any mention of send being ditransitive.
macmillandictionary uses an example to show that it is ditransitive:
send someone something: I’ll send you a copy of the report.
cambridge and oxforddictionaries mention it can be used "with two objects":
[ + two objects ] I'll send her a letter/email/parcel/postcard next week. (cambridge)
[with two objects] ‘he sent her a nice little note’ (oxford)
This does not help much if you want to quickly check if a verb can be ditransitive, because if it is not mentioned, it may still mean the dictionary simply doesn't mention it, even if it is correct to use a verb with an indirect object.
Searching for "ditransitive verbs" does yield several lists of examples, though, like this Australian list. And indeed, that list does not contain explain and suggest.