The Ascending sign depends on where you were born.
Imagine the place that you were born at the time you were born. also imagine no hills or buildings to block your view. You could look around a 360 degree circle, running through the compass points North, South, East, West. This is your local horizon.
Now imagine the point directly above you in space - the Zenith. Think of a circle that runs through this point and is directly aligned North to South. This circle is called the Prime Vertical and will be at right angles to your local horizon. You could use these two circles as co-ordinates to plot everything that lies around, either by is compass baring (often called Azimuth) or its height above the ground (often called declination).
Imagine now that your Horizon is extended and lowered till it runs through the equator (and hence the middle of the Earth). Also running through this extended local horizon will be the Ecliptic - the circle which traces the apparant path of the Sun around the Earth.
OK - we have three circles, horizon, prime vertical and ecliptic. All of these are what is called Great Circles, their centre is the Centre of the Earth. They all therefore intercept. If you follow the Prime Vertical Southwards till it too, cuts the ecliptic. The point where it cuts is called the MC or Midheaven. Where the Prime Vertical cuts the ecliptic in a due north direction is called the IC. It lies 180 degrees opposite the MC.
Also imagine the point where the ecliptic cuts your local horizon in the East - this is your Ascendant. Whilst the MC is due South, the Ascendant is not always due East, but it is in a mainly Easterly direction. It is the point in the East where the Sun rises, as you look at it from your place of birth. As most of the planets line in a reasonably tight band on the Ecliptic, all the other planets, including the Moon will rise at this same point.
180 degrees opposite the Ascendant is the Descendant - the point where the local horizon cuts the ecliptic in the West.
These four points, MC, IC, Ascendant and Descendant form the four angles of your natal chart. Their positions depend on your Latitude and Longitude of birth.
The easy way to find them is through Astro.com or similar. Though you can calculate the positions with the aid of a table of houses, often supplied in introductory Astrology books.
In your case, if you were born between 12 Noon and about 2:15 in the afternoon, your Ascendant will be Leo. If you were born before about 12:20 your MC is Aries, after that it will be Taurus during the two hour time span.
