|A misaligned seam doesn't have to mean unripping the whole piece!|
Next, use a perfectly straight pin (I have a designated pin I received from Kimberly in class that I use only for this purpose) to line up the exact point where the seams should intersect. On a quilt block, you will poke the pin through the exactly accurate 1/4" seam mark of the top piece, then repeat to move the pin through the bottom piece's exactly accurate 1/4" seam mark. The picture below shows the pin perfectly aligned through both layers of piecing.
You will then resew your seam, leaving the pins in until the needle is pretty much right at them. I don't advocate sewing right on over the pins because it's too easy to hit one and break it, possibly damaging your machine or your person in the process.
Your end result should be a perfectly aligned seam. While I've demonstrated this on a quilt block, the process will work the same for a clothing or any other type seam as well. The key is realigning the seams with the vertical pin at the exact intersection.
It may take you a bit of practice to get the process down, but it is really accurate and you don't have to rip an entire seam out to fix one little bit.
Something else I'd like to mention is that it's up to you to decide how close is close enough. Some places don't necessarily need an intersection to be exactly on because they will be camouflaged by the pattern print or location of the intersection. Others, like my super-contrasting intersection pictured above, will be really obvious if they don't line up. Points on a block are important to line up too. Again, it's up to you to decide what constitutes quality.
Here's what I am making:
I have 49 more blocks of 25 squares to make. Finished squares are 1.5". I cut around 1550 of them for this quilt. I may be insane. ;)
One more tip:
You can buy a bamboo stiletto made by Dritz in the quilting notions section of JoAnn. Full price is $8 or so, so be sure to use your coupon. The stiletto is very useful as a guide for teeny-tiny ends of seams. You can hold the seam in place with the end of the stiletto and help guide it under the foot so that the end of your seam doesn't curve. This is especially helpful on tiny block pieces.
If you're wondering what the pink tape is, that is 1/4" tape that I have lined up so that I don't have to mark HST. It's working fairly well for me as long as I'm trimming down the blocks.