Sorry if this is a question that comes up a lot, but my reed is fairly flat, and if I try a tighter embouchure, it does go a bit sharper (I work with a tuner) but still it`s way out of tune. I`m guessing I`d have to shave the reed somehow, but I have no idea how. Would anyone be able to tell me how to make my reed sharper?

You would have to clip the tip to raise the pitch, but only do a very very little at a time till you get a satisfactory raise in pitch... too much clipping can ruin your reed. A little flatness with a relaxed embouchure is okay (if you clip to much you can still try adjust your reed to compensate by shaving the ribs and a little heart).

Also rather than compensating with embouchure pressure to raise the pitch hold out a C and relax and pout your embouchure to flatten the pitch as far as you can... then keep that flat relaxed pout and press the reed against your bottom lip to bend the pitch up. You should be able to bend your pitch upwards and downwards toward the next note with a relaxed embouchure. It may be easier to try on the reed alone first.

Thanks Piko, for your great help!

Glad that helped.

another think.Try to clip the tip of some flat reed to make up to the pich or even a bit sharper!
so you could play with open mouth,relaxing as much as possible to bring it down

Isn`t that what Piko said?

It`s a different approach... I prefer the reed to be at or just below pitch where you can adjust with the reed pressed against your lip (sharping) (while still maintaining a relaxed embouchure!) to compensate for a slightly flat reed while Smith is suggesting adjusting the reed to be sharper than usual and adjust by EXTREMELY relaxing your lips (flatting).

The only problem I have with the sharp reed method is that I find cutting the tip to be risky and would rather have a slightly flat reed that performs well than to risk cutting a little too much off the top.

It may be enough to put a little bit more reed into your lips.

Check the pitch of the reed. Play the reed only in your mouth. Many times oboists test a reed by itself. The reed should sound a B or C.
Check the aperture of the reed. If the opening is large then this makes a flatter pitch. In this case avoid soaking the reed a lot. Gently squish blades together.
Measure the length of the reed. Longer reeds are not always flatter but check it. You will need a metric ruler. 70mm is average length....some people like 68-69 and some longer at 71 or 72.
In addition check how much reed you are putting in your mouth. If there isn`t enough in your mouth you will be flat.

Thank you, for such a detailed explanation!