I usually don't landscape cause I'm bad at it but recently I've been trying to work on it and i noticed few things
1. smaller lots are much easier to landscape cause less space to fill
2. its somehow easier to landscape when you do not center the house on lot
3. fenced areas and bushes are actually pretty cool
4. when in doubt add a big terrace instead so you don't have so much lawn to fill
5. make logical pathways with rocks, terrain paint, floor tiles and such and design around that
6. consider neighbors ideas cause grass is always greener next door - meaning look at other yards in your sims neighborhood