Once you are on Hwy 403 (during rush hour this stretch could be slow to very slow travelling), then after about 3 km, you get to the point where the two separate parts of 403 meet. The trick here is to be in the second lane from the left.
By far, the best point to travel from here on in on the expressways is the second lane from left. This, at most points, automatically leads you to where you want to go. Note that at this point on the 403, the far left lane is reserved for High Occupancy Vehicles, that is, cars with 2 or more people in it. This special lane continues for about 15 km. If traffic is extremely slow, use it, otherwise don't bother, just stay in the middle lane of the three regular lanes.
At this point, about 15 km after Eastgate, about 1 km after Winston Churchill Boulevard, Hwy 407 branches off from Hwy 403. You want to stay on Hwy 403 towards Hamilton. Best point to be is in the middle of the 3 regular lanes. This is the advance warning sign.
This is the actual point where 407 branches off of 403. Stay in the second lane from left. This leads you automatically onto 403 towards Hamilton.
Once you get past the 407 branch off, you need to once again get into the 2nd lane from the left on 403. Then, after about 5 km, Hwy 403 and QEW meet up. You'll see Lake Ontario in the distance and a huge Ford car factory with giant chimneys on left at that point. Slowly work your way over to the 2nd lane from left and stay there. This is what it looks like for the most part on QEW. If your luck is bad, this can be a slow stretch during rush hour.
After about 25 km on QEW, Hwy 403 reappears and branches off from QEW. This is the advance warning sign at Brant Street. Be in the middle lane here.
Make sure that you stick to the right hand side of the middle lane here. That will guide you onto Hwy 403 Hamilton and Brantford.