It was not until I tried using regular playing cards for divination purposes that I realized it helps to know basic numerology; that is, to read the pip cards from a numerological point of view. (This applies to reading Tarot cards with illustrated or non-illustrated minor arcana, too.)
At the time I first read with regular playing cards & for many years after, I had no knowledge of Tarot & only some knowledge of numbers & of astrology. I loosely based the reading of the playing cards on card meanings provided by Maurice Woodruff in his first book which I think was "You and Your World" (long out of print but a later book, "The Secrets of Fortunetelling Your Own Future", can be found via the secondary market).
Also gleaned possible meanings from a couple of very old fortune telling books (unfortunately literally crumbling from age now & from a friend's grandmother & already old whence she acquired them). I do not know the source of Woodruff's meanings; possibly to be derived from that referred to as the traditional &/or gypsy fortune-telling methods but I am not really familiar with either sources.
Utilizing suit associations also helps though Woodruff's books do not mention specific qualities for all the suits. Most of the meanings of pip cards are puzzling in that they do not correspond to anything actually intelligible except perhaps by their numbers & suits. Even with those attributes, the correlation between some cards & their meanings are not clear.
Examples of his meanings follow:
As a suit, Hearts "the luckiest suit in the whole pack" (which I could see since Hearts seem related to the emotional realm).
Ace-Hearts = "a house or residence..."
Ace-Diamonds = "money".
Ace-Clubs = "Nighttime...any time from noon onward."
Ace-Spades = "The unlucky card...right side up indicates sickness. Upside down indicates a death."
9-Hearts = "...most important card in the whole pack...the 'wish' card."
9-Diamonds = "...second best card...another 'wish' card."
10 cards = two of them pertain to security; the other two to business.
A few of the cards represent initials; others specific occasions or events.
Jack, Queen & King = people or individuals based on their colouring.
King-Diamonds = In addition, this also represents "...a doctor or something medical".
King-Spades = "...dentist or a visit to a dentist".
Queen-Swords = "...can sometimes indicate a widow or divorcee".
Since I became involved with Tarot, I also tend to see the cards as quite flexible; to be an inspiration for information as the meanings are not static but to be considered within the context of any throw.
I think this is an interesting website, more comprehensive than others I have seen & forgotten:
http://www.geocities.com/twelveofhearts/intro.html