Take Colour Care; Only buy shades to match your theme or color scheme, or streamers in only one or two matching shades. For example, if you're having a watery theme stick with blue and green. If there's no theme but pink's the birthday girl's favorite colour, buy pink; be it hot, candy or rosey pink. (You can also read more about How To Choose Colour and get yourself a color scheme!)
Hang them in groups; if you're having a jungle party, hang streamers over the front door to enhance the grand entrance, suspend them in one corner to create a hidden den effect, or drape a stair balustrade to recreate over grown ivy. Alternatively, create a sea-like effect as pictured, by placing several strips of each color at equal intervals over the buffet table. For a princess create garlands of streamers over the windows, and so on.
Watch the length; long and over-the-floor-drapey looks great if they won't be a trip hazard, otherwise, stick to shorter lengths. For Mimi's 4th birthday (pictured) we cut three different lengths and stuck them over the table as a grid (it's hard to photograph); Mimi helped me cut 3 pieces of each color about 3-floor-tiles long, and 3 of each were 4-tiles long, and the last 3 of each shade were 5-tiles long, this way there was a cascading effect, with the streamers being longer at the back, it made the effect more dramatic, and we could still fit food underneath.
Twist it up a little; experiment with keeping the streamers straight, twisting them in a sort of spiral effect (works best when both ends are fixed), or tight-twist them every now and then to create a seaweed sort of texture. Go for one type per area, or have a few different textures side by side.
Create a canopy; if you look at Little Lotti's ballet party photos (the tabs at the top of the blog), you'll see how by pinning the streamers at each end we were able to make a 'ceiling' over the lounge room floor, and the girls were able to dance underneath. This instantly created a room, or a world, and they called it their 'dance studio'. the same 'room' effect can be created for any party or theme.
Keep them dry; the worst thing about streamers, is that they are rarely colourfast; as soon as they get damp (think rain, spilt drinks or even yucky fingers), the streamers start to pucker and lose their shape, the dye gets on everything, and it all starts to look a little sad.
Don't be scared of streamers; they're cheap and cheerful in my opinion; simply follow the tips above and have a go - you'll be fine.
So go on... think of an excuse to celebrate, buy some streamers and throw a party!