My yoyo string got all tangled up and crap, so I need a new one. Can I use one of those construction strings that can be bought at home depot?
Construction strings? You mean the kind used to make chalk lines? Haha naw that isn’t that good of an idea… you can make your own using thread from a craft store but it isn’t exactly easy.
String is inexpensive from this store. 100-Pack of Blueprint string for $14. Heck, even Toys r Us carries YoYo string
If you want a terrible experience and a potentially broken yoyo, sure.
There’s another popular yoyo site that has a good vid explaining string tension. See if you can find it or PM me for it and see if that’s your problem first.
A new string? As in you only have one? Lol!
With one post, it’s quite possible, Nathan. I remember having a yoyo and not even knowing you could GET replacement strings. I thought I had to buy a new yoyo every time mine broke. 
Do NOT get chalk line string. It won’t work right.
If you wanna go super cheap, get one of those sewing thread. Make sure it’s either polyester or cotton (poly last longer on bearing yoyos though). Now make 4-6 layers of thread for about 4 meters long, tie one end in something like nail or door handle. Twist the other end clockwise, make sure to keep the string tight or it will mess up. Keep doing this until it feels springy, now take your yoyo and place it in the middle of the string. Bring both the string end together (make sure to keep the whole thing tight or it will mess up), now hang the yoyo up letting it twist the string. Cut the string to your liking and make slipknot, voila! you have a yoyo string. You probably need to experiment a bit about the thickness and how much you need to twist the string.
Otherwise just buy some, they are cheap.
Save $5 at most and spend hours of your life making string. Hm, tough decision…
Hours? I used to make a 10-pack in a little under an hour. Choose a durable thread and it’s like having a pack of Dragon strings or something.
Like what Nathan said, making yoyo string or buying them are the most efficient ways to get yoyo strings.
If you want to make them however, here’s a link on how to make yoyo string:
That guide is the most basic way of doing it. Currently I can make one string for one minute, not everyone are willing to make their own strings though.
Making string isn’t difficult but it’s even easier to just order some. On the other hand, I’ve noticed that there are many that are afraid to experiment with anything! I must say, I have unraveled twine, construction string, many others, twisted up the threads and it worked fine. It may be tedious, boring, but it’s possible.
Sometimes you just have to use what you have and experiment. There’s something to be said for being able to adjust, adapt, and be flexible in one’s thinking.