Welcome to this tutorial on legato! Stay relaxed for this one, folks.
1. Make sure fingers stay as close to the fretboard as possible
2. Steady wins the race - If you play or practice at "your" natural pace with complete accuracy, you will aquire more speed
3. Proper breathing and posture = Stronger player - One of my favorite teachers at Berklee said that more than 90% of music related injuries are due to improper breathing. ;-)
4. Play evenly - One way of doing this is transforming your line into 16th notes and practicing it that way until you build up the endurance to play it faster
*Helpful Hint* - You can try rendering your lines to any sub division as well. So instead of using a metronome you can actually pick a tempo that is comfortable for you, and work your way up in 8ths, triplet 8ths, 16ths, triplet 16ths, etc. This is a way you can intergrate time feel into your playing, making you more versatile.
Thanks for stopping by guys. I wish you all the best!