There are dozens of very good line to line / line to leader knots out there. Most are reasonably easy to tie. What is the best knot for me might not be the best for you. For example, the double uni is an excellent knot for joining two lines but put me out in a boat in the late fall and with the wind and numb fingers I'll never be able to tie one. Look at the link below, bookmark it under "fishing tips" or somesuch and when you have the time, go through them and find which one you're comfortable with. All of the knots listed are good but if you can't tie them properly in the fishing conditions you're in, they're useless. Practice your chosen knots at home 'til they become second nature. Just remember that while you're out fishing you won't always be in ideal conditions.
Here's the link: http://www.netknots.com/html/fishing_knots.html