For laminating, wood surfaces should be thickness planed smooth, leaving the board surface free from machine marks, tear out and snipes. Best results are achieved with sharp knives and equipment that is accurately adjusted and maintained.

When planing harder woods, an effect called burnishing can occur. Burnishing occurs when the board moves through the planer at a slow rate of speed while the cutting knives are operating at a faster rate. Burnishing is realized when not enough material is removed from the board, leaving the surface shiny and slick.
Burnishing seals the board's surface which will reduce adhesive penetration.

Solution

Remove material to the final desired thickness at one time, if possible. If not, sand the board surface with a fine grit sandpaper to open the surface pores and to remove glazed appearance.
To confirm that the surface is suitable for gluing, place a small water drop on the surface. If the drop disperses within a minute or two, the surface will accept glue. If the drop does not penetrate the surface, then the board will not accept the adhesive.

End snipe is the gouging or depression of a board. It can occur at either end of the board, when entering the out-feed roller or in-feed roller.

Solution

Make sure the planer is adjusted to factory specifications. The planer table should be clean and should be waxed and polished with a carnauba wax.
A board that is 8'-12' from the center of the planer will not be held steady on the planer table with just one spring loaded feed roller. To help reduce end snipe, support the end of the board (by hand or by roller stand) slightly higher than the planer bed during in-feed and out-feed.

Achieving wood's final thickness and optimal gluing surface can be done by sanding. After evaluating the wood density and quality of the surface after planing (machine marks, snipes), determine the coarsest grit sand paper possible that won't raise the fiber or grain of the wood (60-100 grit). Then, step up sequentially in grit after each sanding (up to 120-220 grit).

Most often, edge to end joining is used to create a larger flat surface from smaller boards. Joining is the process of connecting boards edge-to-edge or end-to-end with glue and specific joinery techniques. It is usually performed after stock has been thickness planed. Edges need to be free from machine marks, tear out and snipes. Joining ends requires some additional attention since it involves end grain. Blades and knives need to be very sharp to prevent tear out and a coarse surface.

Use a joiner or hand planer

To straighten board edges after sawing, a joiner or hand planer is used to ensure the straightest and flattest surface for gluing.

Achieving the optimal gluing surface should be done by sanding, using a higher grit sand paper (220+) and an edge sander, sanding block or edge sanding jig. Lightly sand to ensure open surface pores and remove any glazing.