Hi - most lawn weeds would be controlled / killed off when you spread something like "evergreen" - look for the moss / weed killer on the labels. Just don't over use as it will scorch the grass...
Regular mowing (make sure the lawnmower blade is sharp)will keep the lawn healthy & will allow the grass to smother out the weeds. When mowing, make sure the grass is dry & never take more than one third of the grass length off in any one mowing.... it's hard to keep a lawn looking good all the time, especially with kids / pets on it... all depends on the look you want against the function that you need the lawn / grass area for...
You can get some lawn sand & some bagged top soil for the "poor areas" to help the grass... make sure to aerate the area & for any bald areas, throw some grass seed on it, rake it in (you can do this from April on)... just don't use the fertliser at the same time of / or after the grass seed is put down...
Another thing I found is defining the border of the grass area to highlight it... make sure grass edge is defined, clean angles for the eye, contrast colours on border areas with flowers / plants... helps define the grass area more... Hopefully we'll get a good summer that can be spent outdoors enjoying the garden!