Sleeves
To give sleeves the correct shape you have to increase stitches while knitting. There's a simple trick to keep this as unobtrusive as possible. At the same time this method prepares the edges for a perfect seam and makes them easy to sew.
How you can calculate the correct increase rhythm can be found in the Knitting Tip CONVERTING PATTERNS

Here's how it goes
Always increase stitches in the right side row, so that you can check the result immediately.
After the edge stitch, work the first stitch in the basic pattern and then increase one stitch - work accordingly at the end of the row.

Stocking stitch: Edge stitch, K1, pick up the cross stitch between the 2nd and 3rd stitch (at the beginning of the row) or at the end of the row between the third and second-last stitch …	… Knit into the back of the stitch. See Knitting Tip TWISTED STITCHES.

This method can be used with every basic pattern. What's decisive for the result is whether you knit or purl the stitch next to the edge stitch and whether the increased stitch is knitted or purled through the back of the loop. Depending on the pattern this can change in the course of increasing, e.g. with ribs. Increasing in the right-side row means you can check your decision and see if you're still in the right pattern.

K2, P2: Edge stitch, P1, pick up the cross stitch between the 2nd and 3rd stitch (at the beginning of the row) or at the end of the row between the third and second-last stitch ...	… and purl into the back of the loop. See Knitting Tip TWISTED STITCHES.

Perfect seams
The edges you get with this method means you can have a neat seam. See Knitting Tip MATTRESS STITCH.

Stocking Stitch: 2 plain stitches come together in the seam. The basic pattern is not interrupted.	Ribs: In increasing the first stitch next to the edge stitch and the increased stitch is coordinated into the pattern.	Variation Ribs: In increasing the first stitch next to the edge stitch is knitted (plain) and then the increased stitch coordinated into the pattern.

Another Tip
Increasing and seams can be pretty. They don't have to be hidden if you follow some basic rules. Be creative! How about a cable pattern along the seam?