Determine the context you are in for the proper phrasing. Realizing that there are formal and informal ways to express love is very helpful in the usage of this phrase. In informal or friendly situations, use the phrase "daisuki desu." The rarely used phrase, "aishiteru," would be applied only to serious, formal situations, which again are rarely used in the Japanese language.
Break up each word by syllables. Let's start with the informal phrase "daisuki desu"--Dai-su-ki de-su or Die-sue-key deh-sue. Next, the formal phrase "aishiteru"--Ai-shi-te-ru or Eye-she-teh-rue. Separating the word into each syllable makes pronunciation easier to handle.
Remember which situations warrant which usage. If you're not sure, ask someone discreetly. You don't want to create an embarrassing situation (see Resources).