Play the Bb4+ lines. I don't know if they're objectively the best, but they're the ones Scandi players seem to hate the most.
Scandinavian defense
A simple setup to play for is with pawns on d4 and c4, knights on f3 and c3, bishops on e2 and e3, queen somewhere like maybe b3 or a4, rooks on d1 and c1. Basically white will play for a central break with d4-d5.
You will hear more complicated explanations, because chess players love to make things as complex as possible.
However based on the level the question is asked, the above will get you started. Only thing to add is that 3.Nf3 is the most precise move to start with.
If you happen to play the Pannov-Botvinnik against the caro-kann 3.Nf3 can get you there.
Really?? I think you mean 3.c4 c6 4.d4 cxd5
Also be prepared for 3.c4 e6 4.d4 exd5 with an exchange French.
3.c4 intending 4.d4 is indeed a very SIMPLE and practical way to make this Nf6 scandinavian completely irrelevant. You instantly transpose to a Panov-Botv or an Exchange French.
3...e6?! is just a bad move as White takes it and is up a pawn, although you should work on tactics to make sure you don't get into trouble here. I think Black doesn't have much compensation, and have won 100% of my tournament games on the White side of this, but 3...c6 should not be taken.
Reasonable minds may differ on the merits of 3...e6. For example, the Houdini engine on my 3.4ghz machine puts it at +0.20 despite Black's pawn deficit and personally i had an 80% score in the Icelandic Gambit Accepted before i sobered up and switched over to 1...e5. Jeremy Silman authored a book in the 1980s suggesting a dubious line for White against the Icelandic Gambit that is actually clearly better for Black.
I would only say that after 1.e4 d5 2.exd5 Nf6 3.c4 e6 now 4.dxe6 is the ambitious way to play for an edge, and 4.d4 would be my personal suggestion to get a simple and easy equalish position with minimal effort based on the infrequency of the variation.
this is the variation i play
did the board not work?
oh well. basically it is 3 b c4 with variations
1. e4 d5 2. exd5 Nf6 3. c4 c6 4. dxc6? (4. d4 transposes into Panov-Botvinnik and is much better) ...Nxc6 leaves black with an edge in development on a wide-open board, solid control over the d4-hole, and easy development - all for a pawn that he will soon win back. I don't have a ton of experience with 3. ...e6, but in the one game that I played it I drew a GM at move 19 in a simul expo. (I would've played on, since I think I was better, but we had been playing for two hours and I was sick and not at all sure how long I could stay awake. That's another story...).
I find the most challenging games (as black) come after 3. d4 Nxd5 4. c4 .
I'm a pretty religious Scandinavian player.
How do I play against this:
I know that I can play d4 Nxd5 c4, but I wonder if there is a simple system against it, even if it only provides equality?