The four cups of wine
What type of wine
- It's perferable to use red wine.  If there's white wine that's better than the red wine, Ashenazim say that one should have the white wine, while Sephardic practice is to have red white anyway. 
- Many authorities say that one may not use grape juice for the Seder, however, if one hates wine or will become ill, then there's is what to rely on to have grape juice.  Others, however, permit having grape juice. 
Making Brachat HaGafen
- The Ashkenazi minhag is to make HaGen on each cup of wine and a Bracha Achrona only on the last one. 
- The Sephardi minhag is to make HaGen on the first and third cup of wine and a Bracha Achrona only on the last one. 
- There’s no Bracha Achrona on the first cup even if one knows that one will take longer than Shuir Ikul in explaining the Haggadah. 
Drinking between the first and second cup
- One is permitted to drink between the first and second cup, however it one should be strict not to wine too much wine so as not to get drunk (and not be able to say the whole Haggadah). 
- According to Ashkenazim, in order to be permitted to drink between the first and second cup one must have had in mind to drink anything that comes later or that the wine was in front of them when he made the bracha (as long one didn’t have in mind not to cover that drink) because in this case no new bracha is needed on the wine between the first and second cup. 
- It’s totally permissible to drinks other than wine or intoxicating beverages between the first and second cup. 
Drinking between the second and third cup
- It’s permissible to drink between the second and third cup. 
If four cups are drunk all at once
- If all four cups are drunk at once and not dispersed throughout the Seder in their proper place one doesn't fulfill his obligation. 
- S"A 472:11
- Rama 472:11 writes that if the white wine is better one can have that instead of the red wine. However, Chazon Ovadyah (Pesach vol 2 pg 11) writes that the Sephardic custom is to use red wine anyway.
- Mikrei Kodesh 2:35 (pg 130), Sh"t Chazon Ovadyah (in the note on pg 99-100), Halachos of Pesach (chapter 20, Sec B 5, pg 222) quoting Rav Moshe Feinstein rule that one doesn't fulfill חירות- having wine as a free man by having grape juice. However, Halachos of Pesach concludes that if one is unable to have wine one should have grape juice.
- Sh"t Mishneh Halachot 10:87, Nefesh HaRav pg 185 in name of Rav Solavatchik
- Rama 474:1
- S”A 474:1
- Halichot Shlomo 9:24
- S”A 473:3 writes that even though it’s permitted to drink but one should be careful not to drink too much wine so as not to become intoxicated and become unable to finish the Haggaddah. Darkei Moshe and Mishna Brurah 473:14 write that such is our minhag.
- Mishna Brurah 473:13 writes that according to Ashkenazim that make a bracha on each cup of wine and making a bracha on wine unnecessarily is forbidden because it looks like one is adding to the established number of cups of the night. Therefore, if the wine was on the table as one made the bracha or one had intention to cover anything that comes later, it’s permitted to drink the cups.
- Mishna Brurah 473:16
- Mishna Brurah 473:12
- S"A 472:8