For chess players who hates memorising opening lines, I recommend you to study some systems. I will give 10 examples of systems here, 5 with Black and 5 with White.
1. The Hedgehog
This system is usually used against the Open Variation in the Sicilian Defence
In this system, black usually aims for d5 and b5 pawn breaks, while also sometimes aims for a kingside attack with Qc7-b8 and Be7-d8-c7.
2. The Hippopotamus
This can be played against any opening. If white is naive enough to attack without enough preparation, the Hippo can counterattack very nicely.
Common themes for black is to respond White's pawn to d5 with e6-e5 followed by f7-f5 attacking the kingside. If white breaks with pawn to e5, black will play d6-d5 followed by c7-c5 with a queenside attack.
3. c6 Pirc
One of the most popular hypermodern systems.
In this system, black usually attack on the queenside with b7-b5, a7-a5, and combined with the g7 bishop, this attack can sometimes be very dangerous, especially with opposite-side castling.
4. Nc6 Pirc
Another variation of the Pirc.
In this variation, black attempts to attack the white center with pieces, following the 'pure' hypermodern style of Nimzowitsch. If white does play d5, the c6 knight will get a nice home on e5.
5. The Hanham Variation of Philidor Defence
Although is usually played through the Philidor Defence move order (1.e4 e5 2. Nf3 d6), it can be played against 1.d4 too.
In this system, black intends to maintain his central pawn on e5. This system is extremely solid but passive.
6. Yugoslav Attack
This is a usual weapon against the Sicilian Dragon, while actually can be used in any case where Black fianchettoes kingside.
White usually exchanges bishops with Bh6, and do a pawn storm with g2-g4 and h2-h4-h5 opening lines. On the other hand, he must be ready for a d5 break from black, and also a queenside counterattack.
7. Colle-Koltanowski System
An easy-to-remember system but can be aggresive if black doesn't know what he is doing.
Typical plan for White is to make the e3-e4 break, and if possible, e4-e5 kicking the black knight on f6, and make a GGS
. A drawback of this system is a locked bishop on c1 if e3-e4 cannot be played.
8. Colle-Zukertort system
This system is probably invented to answer the main drawback of the Colle-Koltanowski system: inactivity of the dark-squared bishop. However, this system has another drawback. The d3 bishop, the White's main attacking piece, cannot avoid being traded if black plays Bc8-a6.
Still a family with the Colle System, but with f2-f4 played.
A drawback in this system is the inactivity of the dark-squared bishop is even more highlighted with the pawn on f4. On the other hand, the f1 rook can join the kingside attack with Rf1-f3-g3/h3.
10. King's Indian Attack
Put simply, this is a mirror image of the King's Indian Defence, but Black's e-pawn usually is not on e5 (while in the KID white has a pawn on e4). White usually goes for a kingside attack with e4-e5 break.
If you have any other systems, feel free to comment on this blog. Thank you!