First recommendation: Buy the cable. If you need longer than you can buy, get a long cable for distance, a short crossover cable, and a CAT 5-rated coupler. If you don't know what you're doing, the cable may pass 10 meg packets jus' fine, but fails at 100Mbps.
If you resist the recommendation to buy, and absolutely, positively just gotta make one yourself:
Make sure all the components you buy are specifically rated for Cat5 (5e, 6). Even the little clear plastic plugs.
The color order is CRITICAL to get full-rated performance:
White-orange, Orange, White-green, Blue, White-Blue, Green, White-Brown, Brown. This order is from the top (clip down), looking from the open end of the connector, from left-to-right. There can be no more than 1/2 inch of wires exposed and/or untwisted (that's TOTAL, beginning at the contact-end of the connector).
The pair-ordering above is for an TIA/EIA 568b cable. If you make both ends like this, you have a straight-through cable. If you use the above pair-order on one end, and swap the orange and green pairs on the other end, you have a crossover cable.
Don't try to clip out unused wires...it's a pain-in-the-butt, makes it difficult to thread the wires into the connector correctly, and blows the certification on the cable.
Good Luck
Scott