I find the two biggest difficulties of a space with this layout are: 1) avoiding the straight-line dictum; and 2) manipulating the space so it's functional for your needs.
The straight-line dictum refers to letting the straight lines of human design — seen in the straight line of the sidewalk, street, fence or even the house foundation — dictate the landscape design. This often leads to a single shrub or perennial species planted in a row parallel to whatever other straight line is present. I'm not saying this can't work, as seen in formal English gardens with impeccably groomed hedges or shrubs, but it's usually a lot of maintenance. Most homeowners will find semi-formal or informal landscapes that sweep and curve more visually pleasing — they help break up the angular layout of the traditional rectangular urban yard.
The latter design dilemma is extremely important to consider when your space is too small to support everything you want to include in your garden design. The first question you should ask yourself is: how to you intend to use the space? Is a grill and large table for gatherings essential, or would you rather have an outdoor lounge/living area with a hot tub? Do you need a space for your children or dog to play, or do you plan to be an urban homesteader? Your yard might be big enough to support a couple activities but chances are good you'll have to narrow it down. Once you've chosen which activities you want to incorporate, you'll need to decide which area of your space is best suited for which activity. The site's individual attributes should dictate what is the best location for a particular function (such as situating your vegetable garden in the sunniest spot or your children's play area in a shady location).
Having the forethought to consider these two common design dilemmas when planning your garden will lead to a visually appealing and functional space.
(Images: As linked above)