I dug and lined mine with a non rigid liner 14 years ago its was guaranteed for 20/25 years and have never regretted it. Go for it I love mine and enjoy it every day.
I have no filter and never use anything but rain water to top up. I get a lot of enjoyment from the fish newts and other pond life it attracts such as the dragon flies.
Take your time deciding where to site it, under trees is not a go idea.
Lots of things to consider, which might be a good place to start such as:
Do I want to see it from a particular part of the house or garden? mine is seen from the dinning room and kitchen.
Do I want it raised above the ground with a surround or do I want it at the same level as the ground? Mine is level with the ground so I can easily see into it.
Do I want it to be filtered or natural? mine is natural.
Do I want it just plants or with fish? mine has both and it had to be deeper in the middle so the fish could safely over winter.
Do I want it surrounded formal or informal just paving or just plants I have a mixture of both.
There are lots of photos of members ponds on the Goypeadia 'Pond ideas' page for you to look at.

The only other point I would make is that if you have small children a pond is perhaps not such a good idea... I remember Bulba 'just' grabbing the hood of younger grandson's jacket as he slid into the pond 15 years ago.

hi thanx for the reply, yuo've certainly give me some good things to think about before starting.
well as for the children side of things fingers crossed mo grandkids coming for plenty many years lol and my youngest is nearly nine years old now and definately no more coming from me so thing we are safe there.
just got to get a cover or something over the pond as i'm aware i have cats and dogs.
to answer some of the questions...
we kind of have a place to site it (its at the end of the garden. there are a few trees the other side of the fence but they are not hanging over the area we want to use)
plus i can see it there from anywhere in the garden, the kitchen and from the sitting room so definately a good site.
not sure about raised level or ground, but given the dog situation (and the fact they are short legged) i am edging towards the raised idea more, but again not sure how to do it.
not sure on filter or natural. whats the pros and cons of both? we had decided that we'd like both fish and plants and were looking at sherbunkin and possibly koi so if i could aim the depths layout towards those breeds think it would be better.
i think i'd prefer paving around it.
think thats everything....thankyou for replyng and i will definately look at the pics on here thanx

Neither dogs nor cats will fall into the pond and, if they do, will swim back out of it. Our nutty Siamese prefer to prink from the pond, or a rain butt, puddle etc.!

I note you say 'plus i can see it there from anywhere in the garden, the kitchen and from the sitting room so definately a good site' - If you raise it you would have to walk right up to it to see it.
One more thing I thought of, you need to consider what you will do with the soil you dig out as it will be a considerable amount depending on size.

a raised pond helps keep a lot of the wind blown rubbish out of the pond . it the trees you want it near drop there leaves youl regret putting it there eventualy . its quit a big question . i mean do you want a natural pond or slightly bigger with fish or realy quit big with koi etc .a photogragh and more idea of what you want would be good . also the raised pond stops you digging so much if at all . i have a 2000 gallon pond with waterfall but did it all raised so know digging apart from footings . my pond is aprox 29" deep all over and being raised i can sit and watch the fish from inches away .i have a pagoda with split bamboo on a roll on top . this stops algi and duck weed and herons and ofcourse leaves as i have a cherry tree hanging over the top .

ps dont skimp on the liner get the best you can ie butil excuse my spelling as theres nothing worse than your istablished pond getting a leek .

you can check my pond out on one of my blogs or look on utbe under nosey potter if youd like .

My Pond is raised a little as if you have a lawn and you want to put Weed & Feed on it you have No worries of it seeping into the pond, I have a picture on My Pic's, also a Good Liner is a must.
I have got to renew mine as the root of a tree I once had has pierced my liner also the sides have caved in, Ha! Doing well arn't I.
Good Luck with yours. Jackie :o)