There's some basics like everyone mentioned above which is vital on a 3D model. Of course there are lots of other things to do also but their a little more cumbersome like for instance sanding the trailing edges of the control surfaces completely blunt to induce drag on the TE, and then of course counter balancing all the control surfaces.

Key factor even with all the counter measures on a 3D model is simply this. THROTTLE MANAGEMENT!. I can't stress how important that is, when the plane reaches straight and level you should already be at half or cruising throttle (Sometimes even 1/4...btw you have too much power when this is the case! NICE), as soon as the nose pitches down towards mother earth the engine should be at idle already. As you gain more experience you'll discover where you can push the limits a little with the throttle but most 3D models are so overpowered you can really only go to full throttle when the nose is pointing all the way up or if you are doing manuvers where all the control surfaces are loaded up (Flat spins and things).

Like mentioned above, get a very small pitch prop to help prevent the plane from picking up speed. Manage the throttle still!!!. Always use decent control hardware, nothing less than a Futaba/JR super horn on the servo side and use the furthest hole out on the surface's control horn barring you can get the surface throw you need as is. Dual rates and things at max when doing this! Use a decent linkage system which is absolutely slop/play free, ball links come to mind here but honestly a decent clevis and pushrod will work in this scenario. And then lastly be sure to seal the hinge gaps between the control surface and the surface itself with either covering or some self adhesive tape (Packaging tape works btw).

Cheers
Spacey