You should have the right kind of palette to start off with. Your palette should be non-porous to prevent absorption of oil from the paint. Palettes come in a variety of different materials from glass to wood. My personal preference is the BOB ROSS Clear Palette. I have found this palette the easiest to clean and best for mixing colors.
When you are first starting out, it may be a good idea to start with a fairly limited palette of colors. If you purchase every color under the sun, you may find yourself mixing too many different colors, which will result in a muddy painting. Start off slow in the beginning, then add more colors as you become more experienced. Color choices for a limited palette vary from artist to artist. Here are the colors of my palette: Yellow Ochre, Cadmium Yellow Pale, Alizarin Crimson, Cadmium Orange, Phthalo Blue, Burnt Sienna, Burnt Umber, Cadmium Red Medium, Phthalo Green, Titanium White, Ivory Black. I recommend purchasing 1.25 oz tubes of all colors except Titanium White. Purchase a larger tube of Titanium White, as you will be using more of this color.
First, you should get into the habit of laying out your colors the same way every time you paint. This is just good practice and keeps the painting process flowing nicely. Arrange your colors along the edges of your palette leaving a lot of room in the center for mixing.
Don't be afraid to squeeze out a good amount of paint, especially your whites. You will be more productive if you aren't continuously stopping to squeeze out more paint.
Make certain to include all of the colors you think you will need to complete that session of painting as well. Again, this will make you more productive.
When adding paint to the palette, I have found that squeezing the paint out in long lines, as opposed to puddles, keeps my colors cleaner. When you have puddles of paint, they tend to get soiled by other colors when mixing. With a long line of paint, you can just take paint from the end as needed and not dirty the rest. Keep some rags or paper towels handy for wiping your palette knife clean.
It's a good idea to continuously wipe your palette clean during the painting process. There is nothing more frustrating then trying to remove dried up oil paint. Keep some alcohol handy so that you can keep the mixing area of your palette clean.
I hope these tips have helped. Happy Painting!