1.  The Peace Arch Crossing  This is the main border crossing, and it's simple--just stay on Interstate 5 and the expressway will come right up on this crossing.  The downside to using this crossing is that because this is the main crossing to Vancouver, the border delays (when present) are almost always longer than any other crossing point.   
2.  The Pacific Hwy. Border Crossing, also known as the "Truck Crossing".  This exit usually has fewer delays than the Peace Arch crossing, and it's just off the main highway, so it's quite convenient, too.     
3.  The Crossing at Aldergrove.  The benefit of this crossing is that it will consistently have the least wait of any of the main border crossings--so it's a great choice on long weekends or other times when the border traffic is particularly heavy.  The downside to this border crossing is that it's further east than the other two crossings, so you'll want to make the decision for this crossing as you near Bellingham.     

In order to decide which crossing is quickest, you can tune your radio to News 1130 Radio (at 1130 on your A.M. dial), which gives you traffic updates including news on border crossing delays "on the ones"--that is 1 minute past the hour, 11 minutes past the hour, and 21, 31, 41, and 51 minutes past the hour.  If there are significant border delays, you should be able to hear them on this station.   

Border note:   To save yourself any hassles at the border, bring passport or other proof of citizenship and don't bring any guns, alcohol, or tobacco. 

To take the Pacific Hwy Border Crossing, you'll get off I - 5 at exit 276, which is Avenue D in Blaine, Washington.  You'll drive about 10 blocks to 12th Street (Hwy. 543), then turn left.  This will take you to the border.  After you cross, you'll find yourself on Hwy. 15, also known as 176th Street in Surrey.  Stay on that road from O Avenue (the border) all the way north until you get to 96th Avenue.  (The Avenue numbers get larger as you head north.)  Shortly after 96th Avenue, you'll see a sign for Hwy 1 (the Trans-Canada Highway).  You'll pass over Hwy 1, then get on it heading west.  Traveling along Hwy. 1 West, you will take the next exit, Exit #50 (at 160th Street) to the right.  After you exit the freeway, bear left.  You'll pass over the freeway via an overpass to 104th Avenue West.  Continue on 104th Avenue past 160th Street to 152nd Street and turn left.   Proceed down 152nd Street (south) a short distance to 102A Avenue (at the corner with McDonald's) and turn left.  Go one short block down 102A Avenue and turn right on 152A Street.  We are located on the left-hand side of the street at Suite 102, 10190-152A Street on the street level.  Look for the sign Achilles Foot Health Centre.  There is free street parking and free parking in the parking lot behind the building. 

To take the Aldergrove Border Crossing, (which you'll only want to consider if the other borders have length delays), you'll probably wish to make this decision as you near Bellingham.  After you pass downtown Bellingham, you'll find yourself nearing a sign for Bellis Fair Mall.  This mall is located at a Meridian Street, or Hwy. 539.  You'll take that north past the pretty town of Lynden directly to the Canadian border.  Once you cross the border, you'll find yourself in Canada on 264th Street heading north.  Take 264th Street from the border (0 Avenue) north to 52nd Avenue.  Just past 52nd Avenue, you'll reach Hwy. 1, (the Trans-Canada Hwy).  Get on Hwy. 1 heading west.  Traveling along Hwy. 1 West, you will drive from 264th Street across the entirety of Langley and most of Surrey.  You'll pass exits for 200th Street and 176th Street.  You'll take the next exit after 176th Street, which is Exit #50 (at 160th Street) to the right.  After you exit the freeway, bear left.  You'll pass over the freeway via an overpass to 104th Avenue West.  Continue on 104th Avenue past 160th Street to 152nd Street and turn left.   Proceed down 152nd Street (south) a short distance to 102A Avenue (at the corner with McDonald's) and turn left.  Go one short block down 102A Avenue and turn right on 152A Street.  We are located on the left-hand side of the street at Suite 102, 10190-152A Street on the street level.  Look for the sign Achilles Foot Health Centre.  There is free street parking and free parking in the parking lot behind the building.