On our trip to Scotland we took a little day trip to Edinburgh, and I managed to peek into K1 yarn shop. I bought some Scappa yarn in the colours Iona Marble and Scotch Pine. I decided to make a short sleeved jumper for my girl who is eight months old. At that age they are crawling about much on the floor, which can be a slidy affair with long sleeves. If made slightly big it can be used as a tunic at first. As your kid grows, it can be used as a jumper. This is roughly how I made mine:
Pick a jumper or cardigan for measuring and comparing, either in a size that fits at the moment, or a bigger one to grow into. Measure the bottom edge. Find your gauge, and cast on the amount of stitches you need to achieve the right size on a round needle. Knit garter stitch in any colour combination you would like. (I made a stripy pattern by knitting two rows with colour A, and four rows with colour B, and reversed the colour scheme halfway.) Knit up to the point where you think you can start with the arms.
As you reach the armholes, mark one stitch on each side. Increase with two stitches under each arm every second row (on each side of marked stitch). Repeat two times. Total increase: 12 stitches.
Now you will start knitting back and forth, the back and front separate. Start from left armhole. Before turning your work around, cast on three stitches. Turn work, and knit to right armhole, cast on three new stitches before turning work again.
Continue straight till you feel you have the right width for the arms. (Or knit on a bit longer for wider sleeves.)
(If you wish for the neckline to drop slightly at the front, find out the amount of stitches to keep for the collar, and keep it on the needle while knitting four extra rows on each shoulder.)
Knit the backside the same way as the front. Knit it straight up, without any neckline shaping. (The back should have the same amount of rows as the shoulders of the front.)
Keep the same amount of neckline stitches on the back piece as on the front.
Cast off the shoulder stitches and sew front and back together, OR graft the stitches together. (If you want to button the shoulders instead, simply cast off each piece, sew on buttons and make loops. This gives you the chance to make a smaller neckline.)
Now, you should have your neckline stitches left on your needle. If you knitted extra rows to shape the neckline, pick one stitch from each row on each side. I made a roll neck by knitting sock stitch for about 8 rows. (Dependig on the width of the neckline, you might have to use 4 or 5 sock needles for this.)
Pick up the stitches around the armhole with sock needles. Knit a few rows to make a nice edge, or knit on to make a proper sleeve.
Fasten threads, do a quick soak, spin and let it dry flat, and it is ready for the lucky new owner!