For Marriage 2nd, 7th and 11th house of a person`s horoscope are considered. 2nd house represents your family life, 7th house shows your marriage prospects and 11th house shows your hopes & wishes. If your wish is to get married right now, then 11th house will show if your hopes-&-wishes will come true in your life. Now, depending upon your ascendant/your first house/your rising sign, we will be able to see which sign is ruing these three houses.
If you are a cancer ascendant or cancer rising sign during the time you were born, then your 2nd house will be ruled by Sun (LEO), 7th house will be ruled by Saturn (Capricorn) and 11th house will be ruled by Venus (Taurus), judging from these three planets and the condition of them in your horoscope one can see if you will or will not get married, then, to see the timing of your marriage an astrologer will see when these three planets are going to transit into these three houses in your life.
Remember, Planets in your horoscope are always moving, so when Sun, Saturn and Venus come into any of these houses (2nd, 7th, 11th) in any order, they will trigger the marriage aspect of your life, so if Saturn is in Leo, and Sun is in Taurus, and Venus is in Capricorn transiting together for may be 30 days when you turn 26, then this 30 day time period when these three planets are aligned your marriage can be predicted.
Another important asepct to judge your or someone else's marriage is by looking at their 'Dasha' or time period of a planet. In each one of our lives we are being ruled by a certain planet for certain period of time. You might be ruled by Moon right now for 10 years, then Mars for 7 years, then Rahu for 18 years, so if you're going through your Mars 'Dasha', and Mars rules your 7th house in your horoscope as in your 7th house is Aries or Scorpio, then this will give a major clue if you will get married in this time period or not, but only if your are looking at this period after the age of 18.
Also it is important to look at the significator of marriage which are planet Venus and Jupiter. When Jupiter and Venus are transiting through your 7th house or aspecting your 7th house from a certain house, then, that, too, triggers prospect of marriage, since Venus and Jupiter are positive planets representing growth and love, and when 7th house is being looked by Jupiter the planet of expansion and growth, then that house will be blow up like a balloon and you will see how marriage becomes an important aspect in your life.