Even the best tool can fail; always use a continuity tester after crimping to verify the pinout. If you'd like to narrow this down, let me know: Are you wiring an entire house or just repairing one cable ?
Keep the pairs twisted as close to the connector as possible to reduce interference (crosstalk). best buy rj45 crimp tool
Do you prefer connectors (easier for beginners) or Standard connectors? What is your budget range for the tool? Even the best tool can fail; always use
Ratcheting mechanism ensures a complete crimp cycle every time. Includes built-in wire stripper and cutter. Even the best tool can fail