Go with the grain on curves to prevent splinters
Tearout in wood end grain can be reduced by going with the grain. For the vertical grain shown, plan to feed to the top of a curve, stopping there. Routing against the grain causes splinters. The hand router is shown pointing away, as if you were looking through the machine. The table router is fixed facing up and the lumber moves past it.
Routing pine softwood, veneer or stringy luan plywood is difficult. If a bit digs in, the wood grain will split and tear out. For a tactile demonstration of how it happens, roll up a paperback book to fan it out. As you stroke your finger across, it feels silky and sounds like a zipper. If you drag against it, it feels rough and catches. You want the bit to enter so the soft layers ahead of it compress together.
Prior to cutting out a blank or putting on a template, orient it on the wood grain for the most advantage. If your layout has horizontal grain, you could manage it another way, as seen here. A re-arranged perpendicular layout is not always a favorable option. Consider where it would be logical to flip the board over. It's less trouble to methodically re-apply a template than to re-do problem curves ruined by blowout. Reversing the action can also be done by switching between hand and table. Difficult curves could be completed effectively by a drum or spindle sander.
Pressure
Do not press too hard against the template. Take several strokes to work in gradually. Aggressive passes in hardwood are more difficult than in softwood. If you're getting ready to use a large profile bit, rough out the shape with other tools first. On the last pass, engage the full profile lightly.
Heavy pressure can momentarily slow the speed of a weak motor. At the moment it slows, gouging is likely. If you can hear it struggling, that's a good clue the bit is over the hill. If you've been using the same one a long time, it gets less able to cut without gouging.
Feed rate and tearout
A slow rate makes a neater cut. On a scrap of the same material, practice even, steady stroking until your cuts stop tearing out. Hard, dense oak lumber is cut at a slower speed than soft, porous materials. There are exceptions. Solid surface is very dense. Paradoxically, slow feed can make it bumpy. It's not exactly tearing; flakes of plastic adhere to it.
Router bit flutes
The number of flutes varies on different kinds of router bits. A single flute feeds fast but may tend to cut rougher than two straight flutes. A straight flute is common, but it is not the only kind. Shear flutes lean a little.
If a guide bearing isn't needed, consider solid carbide spiral bits. A slow spiral bit twists around in a helix. Spirals have a modest capacity. While an upcut spiral twist bit lifts waste up and out, it may promote chipping on the top of LPL. A downcut spiral is pressing in and avoiding top splintering. To preserve both faces of melamine laminate, try a compression spiral bit. It has opposing spirals to shear both ways simultaneously. This style is more costly.
Laminate chip-out
Manmade composites have even density and no grain to splinter, which makes them popular for routing. They are so abrasive that tools wear out fast. Have a spare flush trim bit available when you really need it. Wherever you can't afford the risk of chip-out spoiling laminate, switch to a fresh one for the final pass.
Vibration
Router bits shouldn't vibrate noisily; they should hum. Vibration causes tearout to worsen. Running the motor faster may magnify it. If it does not improve, blow out the debris and try remounting it. Steady a panel that is rocking or bouncing in response. If a wide profile vibrates excessively, it might be due to weight imbalance. A tall bit tends to bounce and flex near the tip, so choose one no longer than necessary.
Runout
Router bit tearout and noise may be a sign it's out of round. Look for uneven wear. A routed groove with a width greater than the width of a bit that made it may be evidence of runout. Only occasionally can you correct it by remounting it in a different orientation. Make inspection with a dial indicator to see if it is within a hair or .003 in. Touching up the flute profiles can worsen runout.
Fence
Intricate shapes such as stile and rail may be improved by a matching fence clamped over the opening in the standard fence. It can be homemade to come very near to a bit and extend as far as necessary. Use a bandsaw to rough out the middle of the cutout to clear the top of the cutter. Secure it then advance until a precise cutout straddles the bit and only the profile protrudes.