@Neil Kermstrong First... To help stop it flipping. Make sure your Center of Mass is near the top (pointy end) and your Centre of Drag is nearer the bottom (hot end). You can also add fins at the bottom to help too. Basically copy a dart, heavy bit at the front, fins at the back. Even without fins the dart will still fly point first, your rocket is the same, fins will give it a bit more stability, but you won't always need them, and they add drag too.
Second... To help with wobbly rockets. If you haven't done it already, switch on 'Advanced Tweakables' in the main menu game settings, this gives numerous extra features. For this particular problem though, when building right click a part to open the option window, options for 'Rigid Attachment' and 'Auto Strut' will be available (iirc they may also be available in flight). Experiment with those, I use them all the time.
A simple experiment to illustrate the need for 'heavy at the top' is to balance a sweeping brush on your finger. With the brush end resting on your finger (heavy at the bottom) it is very hard to balance, but with the brush (heavy) end at the top it is far easier to control. Wobbly rockets tend to be more prone to flipping too as the thrust keeps moving about relative to the CoM, like a random, uncontrollable gimballing effect.
Hope that helps.