one thing i would suggest - make sure you have a contingency plan just in case it rains - the last thing you want is to be looking fantastic in your wedding gown, hair and makeup - and find it's all been destroyed by the weather! hopefully you won't need it - but it's always better to be safe than sorry. we decided that, if it rained, we'd head to our reception venue early, but sometimes that's not possible...!
i think the other suggestions have been fantastic. make yourself a budget and stick to it. we did everything ourselves, from the invites (which i've since been employed to do another 3 weddings, so they must have been ok!), guest gifts, place cards, through to the centrepieces we had on the tables... we did almost everything on a budget - though dress and photographer were open slather!
definitely decide on your theme and colors before picking your flowers - and look at LOTS of options. i'm a tall person, so had a sheath rather than a tear drop - worked so much better for me - and i wasn't feeling like i had to hold it in a particular way - it was simply cradled in my arms. my bridesmaids also had a sheath - i'd been in a couple of weddings and always felt uncomfy trying to work out how to hold the flowers so they were in the right place and comfortable! also decide in advance if you're going to keep the flowers and have them dried out at home or preserved (freeze dried) professionally - if so, you'll need to arrange someone to get them to the appropriate people as soon after the wedding as possible. it's also something you'll need to get a price on so that you can budget for it - i figured, seeing flowers CAN be a big expense, i wanted to be able to keep them!
decide in advance if you're going to hire or buy your centrepieces we gave each couple a home made CD of music from the wedding as their gift - again, we made them ourselves. think it cost about $50 in total including discs, stickers to label them, cases and the paper for the covers. we included one of the readings for our wedding on the front cover, and a message thanking everyone for attending on the inner cover (got our thank you's out of the way in advance!)