How to increase knitting without leaving hole?

As an experienced knitter who struggled with this exact issue, the key is using the right increase methods. My favorite is the "knit front and back" (KFB) method - you knit into the front of the stitch as normal, but before slipping it off the left needle, you knit into the back loop of the same stitch, then slip it off. This creates a nearly invisible increase. Another great technique is the "make one" (M1) method where you use the left needle to pick up the horizontal strand between stitches from front to back, then knit through the back loop. Both methods create clean increases without those pesky holes that yarn-over increases leave.

From my knitting teaching experience, preventing holes during increases comes down to choosing the right technique for your project. The bar increase (knitting through front and back) is excellent for most situations, but if you're really concerned about visibility, try the lifted increase - where you knit into the stitch below the next stitch on your left needle. For garter stitch, the backward loop cast-on method works beautifully. The common mistake beginners make is using yarn-over increases in places where they're not part of the pattern design. Practice these techniques on swatches first - after a few tries, you'll get that smooth, hole-free fabric you're aiming for.