My method was easy as pie. I couldn't measure using the pipettes because the stuff was so thick.
I ordered an empty 60 ml bottle to make my "stock" in. I ordered 125 ml of 60 mg Nic
juice and 250 ml of VG. You will want to order a bottle of PG too though, since you want the throat hit.
I used tablespoons for measuring my liquids. One Tablespoon is 15 ml . I chose 60 mg Nic to start because I knew it would be very easy to turn it into 30 mg, 20 mg and 15 mg, 12 mg, 10 mg in different batches.
To make my 15 mg juice, I put in 1 Tbs of 60 mg Nic and 3 Tbs of VG. You would do 1.5 tbs VG AND 1.5 tbs PG.- a 1:3 ratio
To make 20 mg nic juice, you would put in 1 Tbs 60 mg Nic juice to 1 Tbs VG AND 1 Tbs PG to get you to 20 mg stock- a 1:2 ratio
I just made my brother some and he wanted 24 mg. I did the 20 mg recipe above and added 1 teaspoon more of the 60 mg nic juice. That got him to 23.3 mg.
I ordered a bunch of 6ml squirt top bottles. I pour my stock from my 60ml -15mg juice into those lil bottles and then add the flavorings to those. It makes it so easy

My 60 ml stock last me about 3 weeks so I don't have to worry about making juice all the time.
If you are ordering 100 mg Nic juice to start, I would suggest making your stock in a 100 ml bottle. It will make measurements easier to figure out easily in your head.
Make sure you wear gloves! make sure you shake all your bottles vigorously before mixing-especially the high mg Nic juice! And shake your stock well after mixing.
Let me give you a hint too. I just found Perfumer's Apprentice and they sell flavoring samples for $1.40 for 4 ml! Meanwhile, I have spent $110.00 on 16 flavorings in the last month because I didn't know I could get sample sizes for that cheap! So go crazy on flavorings but get the small sizes!
Good luck to you! DIY is dirt cheap to do! Excluding those 16 flavors, it costs me @25 cents a day to vape in juice costs!
Lori