What I like is to just kind of plan it out a tiny bit. Envision how it will look once grown in and plan accordingly. Tanks don't always look super nice right when they are planted, once the plants establish themselves, it will look nicer.
Some simple aquascaping tips... You want to group your plants with their species. Plants in the wild will almost always be by the same species, don't have 1 or 2 bunches here then another somewhere else. Plant in groups. Also, plant the tall plants/plants that grow tall in back, lower plants up front. This enables you to see in the tank. Also, slope the substrate, lower in the front taller in back, I would say about 1.5 inch or so in front (2 with gravel) and go at least an inch higher in the back and form a slope. This will give you more depth in the tank.